var popup= new esri.dijit.PopupMobile(null,dojo.create("div")); 
   
//Create map object.  Set nav to true to enable pan buttons.
map = new esri.Map("map", {
      nav: false,
      slider: true,
      displayGraphicsOnPan: true,
      infoWindow:popup
});
dojo.place(popup.domNode,map.root);
var popupTemplate = new esri.dijit.PopupTemplate({
         title: "{NAME}",description:"{DESCRIPTION}"
});
greenLayer = new esri.layers.FeatureLayer(greenURL,{mode:esri.layers.FeatureLayer.MODE_ONDEMAND,outFields: ["*"],infoTemplate:popupTemplate});
map.addLayer(greenLayer);var template = new esri.dijit.PopupTemplate({title:"{NAME}",description:response});
feature.setInfoTemplate(template);
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>  
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=7, IE=9" />
    <!--The viewport meta tag is used to improve the presentation and behavior of the
    samples on iOS devices-->
    <meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no"/>
    <title>
      Flickr
    </title>
    <link rel="stylesheet" type="text/css" href="http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/dojo/dijit/themes/claro/claro.css"/>
    <link rel="stylesheet" type="text/css" href="http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/esri/dijit/css/Popup.css"/>
    <link rel="stylesheet" type='text/css' href='http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/esri/dijit/css/PopupMobile.css'/>
    <style>
      html, body { height: 100%; width: 100%; margin: 0; padding: 0; } .esriScalebar{
      padding: 20px 20px; } #map{ padding:0;}
    </style>
    <script type="text/javascript">
      var dojoConfig = {
        parseOnLoad: true
      };
    </script>
    <script type="text/javascript" src="http://serverapi.arcgisonline.com/jsapi/arcgis/?v=2.4">
    </script>
    <script type="text/javascript">
      dojo.require("dijit.layout.BorderContainer");
      dojo.require("dijit.layout.ContentPane");
      dojo.require("esri.map");
      dojo.require("esri.layers.FeatureLayer");
      dojo.require("esri.dijit.Popup");
      dojo.require("esri.dijit.PopupMobile");
      var map;
      var featureLayer;
      var resizeTimer;
      function init() {
        //setup the map's initial extent 
        var initExtent = new esri.geometry.Extent({"xmin":-16305479,"ymin":-635073,"xmax":5884495,"ymax":8307447,"spatialReference":{"wkid":102100}});
        //create a popup to replace the map's info window
        var popup = new esri.dijit.PopupMobile(null, dojo.create("div"));
        map = new esri.Map("map", {
          extent: initExtent,
          infoWindow: popup
        });
        
        dojo.place(popup.domNode, map.root);
        //Add the imagery layer to the map. View the ArcGIS Online site for services http://arcgisonline/home/search.html?t=content&f=typekeywords:service    
        var basemap = new esri.layers.ArcGISTiledMapServiceLayer("http://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer");
        map.addLayer(basemap);
        //create a feature collection for the flickr photos
        var featureCollection = {
          "layerDefinition": null,
          "featureSet": {
            "features": [],
            "geometryType": "esriGeometryPoint"
          }
        };
        featureCollection.layerDefinition = {
          "geometryType": "esriGeometryPoint",
          "objectIdField": "ObjectID",
          "drawingInfo": {
            "renderer": {
              "type": "simple",
              "symbol": {
                "type": "esriPMS",
                "url": "images/flickr.png",
                "contentType": "image/png",
                "width": 15,
                "height": 15
              }
            }
          },
          "fields": [{
            "name": "ObjectID",
            "alias": "ObjectID",
            "type": "esriFieldTypeOID"
          },{
            "name": "description",
            "alias": "Description",
            "type": "esriFieldTypeString"
          },{
            "name": "title",
            "alias": "Title",
            "type": "esriFieldTypeString"
          }]
        };
        //define a popup template
        var popupTemplate = new esri.dijit.PopupTemplate({
          title: "{title}",
          description:"{description}"
        });
        //create a feature layer based on the feature collection
        featureLayer = new esri.layers.FeatureLayer(featureCollection, {
          id: 'flickrLayer',
          infoTemplate: popupTemplate
        });
        
        //associate the features with the popup on click
        dojo.connect(featureLayer,"onClick",function(evt){
           map.infoWindow.setFeatures([evt.graphic]);
           map.infoWindow.show(evt.mapPoint);
        });
        
        dojo.connect(map,"onLayersAddResult",function(results){requestPhotos();});
        //add the feature layer that contains the flickr photos to the map
        map.addLayers([featureLayer]);
        
        //resize the map when the browser resizes - view the 'Resizing and repositioning the map' section in 
        //the following help topic for more details http://help.esri.com/EN/webapi/javascript/arcgis/help/jshelp_start.htm#jshelp/inside_guidelines.htm
        dojo.connect(map, 'onLoad', function(theMap) {
          dojo.connect(dijit.byId('map'), 'resize', function() { //resize the map if the div is resized
            clearTimeout(resizeTimer);
            resizeTimer = setTimeout(function() {
              map.resize();
              map.reposition();
            }, 500);
          });
        });
      }
      function requestPhotos(){
         //get geotagged photos from flickr
        //tags=flower&tagmode=all
        var requestHandle = esri.request({
          url: "http://api.flickr.com/services/feeds/geo?&format=json",
          callbackParamName: "jsoncallback",
          load: requestSucceeded,
          error: requestFailed
        }, {
          useProxy: false
        });
      }
      
      function requestSucceeded(response, io) {
        //loop through the items and add to the feature layer
        var features = [];
        dojo.forEach(response.items, function(item) {
          var attr = {};
          attr["description"] = item.description;
          attr["title"] = item.title ? item.title : "Flickr Photo";
          var geometry = esri.geometry.geographicToWebMercator(new esri.geometry.Point(item.longitude, item.latitude, map.spatialReference));
          var graphic = new esri.Graphic(geometry);
          graphic.setAttributes(attr);
          features.push(graphic);
        });
        featureLayer.applyEdits(features, null, null);       
      }
      function requestFailed(error) {
        console.log('failed');
      }
      dojo.ready(init);
    </script>
  </head>
  <body class="claro">
    <div data-dojo-type="dijit.layout.BorderContainer" data-dojo-props="design:'headline'"
    style="width: 100%; height: 100%; margin: 0;">
      <div id="map" data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region:'center'"
      style="border:1px solid #000;padding:0;">
      </div>
    </div>
  </body>
</html>
					
				
			
			
				
			
			
				
			
			
			
			
			
			
		I believe you should be setting "content" not "description".
Here's an example that shows using the PopupMobile with the PopupTemplate:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta name="viewport" content="width=device-width, height=device-height, minimum-scale=1, initial-scale=1, maximum-scale=1, user-scalable=no"/>
        <meta name="apple-mobile-web-app-capable" content="yes" />
        <meta name="format-detection" content="telephone=yes">
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <title>PopupMobile Testing</title>
        <!-- MOBILE STYLESHEET -->
        <link href='http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/dojo/dojox/mobile/themes/iPhone/iPhone.css' rel='stylesheet'>
        <link href="http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/dojo/dojox/mobile/themes/buttons.css" rel="stylesheet">
  <link rel="stylesheet" type='text/css' href='http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/esri/dijit/css/Popup.css'/>
  <link rel="stylesheet" type='text/css' href='http://serverapi.arcgisonline.com/jsapi/arcgis/2.4/js/esri/dijit/css/PopupMobile.css'/>
        <style type="text/css">
            html, body {
                height: 100%;
                margin: 0px;
                padding: 0px;
                width: 100%;
            }
        </style>
        <script type="text/javascript">
            var djConfig = {
                parseOnLoad: true
            };
        </script>
        <!-- Script/API Imports: Esri JS API -->
        <script type="text/javascript" src="http://serverapi.arcgisonline.com/jsapi/arcgis/?v=2.4compact">
        </script>
        <!-- Beginning of JS Code -->
        <script language="JavaScript" type="text/javascript">
            djConfig = dojo.config;
            
            //Dojo imports
            dojo.require("dojox.mobile.parser");
            dojo.require("dojox.mobile");
            dojo.requireIf(!dojo.isWebKit, "dojox.mobile.compat");
             
            
            //Esri imports
   dojo.require("esri.layers.FeatureLayer");
   dojo.require("esri.dijit.PopupMobile");
   dojo.require("esri.dijit.Popup");
   
            //GLOBAL VARS
            var service = "http://env-gisdev1.uwaterloo.ca/arcgis/rest/services/green-features/green-viz/MapServer";
   var greenURL = "http://env-gisdev1.uwaterloo.ca/arcgis/rest/services/green-features/green-viz/MapServer/1";
   
            var map;            
   
            //INIT
            function init(){
            
    var popup= new esri.dijit.PopupMobile(null,dojo.create("div")); 
   
                //Create map object.
                map = new esri.Map("map", {
                    nav: false,
                    slider: true,
                    displayGraphicsOnPan: true,
     infoWindow:popup
                });
    dojo.place(popup.domNode,map.root);
     
                baseMap = new esri.layers.ArcGISDynamicMapServiceLayer(service);
                map.addLayer(baseMap, 0);
    
    var popupTemplate = new esri.dijit.PopupTemplate({
     title: "{NAME}",
     description:"Descriptive text should go here: {DESCRIPTION}"
    });
    greenLayer = new esri.layers.FeatureLayer(greenURL,{
     mode: esri.layers.FeatureLayer.MODE_ONDEMAND,
     outFields: ["*"],
     infoTemplate:popupTemplate
    });
    map.addLayer(greenLayer);
            }
  
            //Run the initialize function when the document loads
            dojo.addOnLoad(init);
        </script>
    </head>
    <body>
        <!-- MAP VIEW -->
        <div id="mapView" dojoType="dojox.mobile.View" style="width:100%;height:90%" selected="true">
            <h1 dojoType="dojox.mobile.Heading">Popup Test
   </h1>
            <div style="width:100%;height:90%" id="map">
            </div>
        </div>  
    </body>
</html>
    greenLayer = new esri.layers.FeatureLayer(greenURL,{
     mode: esri.layers.FeatureLayer.MODE_ONDEMAND,
     outFields: ["*"],
     infoTemplate:popupTemplate
    });
        
        //associate the features with the popup on click
        dojo.connect(greenLayer,"onClick",function(evt){
           map.infoWindow.setFeatures([evt.graphic]);
        });
        
    map.addLayer(greenLayer);
					
				
			
			
				
			
			
				
			
			
			
			
			
			
		Popup and PopupMobile work with a set of features. Modify your code to listen for the feature layer's on click event and when it fires associate the current features with the popup.greenLayer = new esri.layers.FeatureLayer(greenURL,{ mode: esri.layers.FeatureLayer.MODE_ONDEMAND, outFields: ["*"], infoTemplate:popupTemplate }); //associate the features with the popup on click dojo.connect(greenLayer,"onClick",function(evt){ map.infoWindow.setFeatures([evt.graphic]); }); map.addLayer(greenLayer);
map.infoWindow.show(evt.mapPoint);
