In case you use the webappbuilder, I created this: ArcGIS Web Application
For the WebApp Builder, there's also the Coordinate Conversion widget from the Solutions team that might be useful some people reading this geonet question. This widget converts input coordinates to various notation formats like MGRS for example. https://github.com/Esri/solutions-webappbuilder-widgets/tree/dev/CoordinateConversion
To play with it, go to http://esri.github.io/solutions-webappbuilder-widgets/ - "Coordinate Conversion" is the third widget.
Well thats better than my widget