Hi all, I just put together a quick widget for adding a zipped shapefile to a webmap as a new operational layer. This is very helpful with custom geoprocessing services that need a feature/operational layer as input. I essentially just wrapped the AddShapefile jsapi sample from Esri so the interface is pretty simple so you can customize the html as needed.
You can download or fork it on GitHub: https://github.com/URSpatial/WAB_AddShapefile
Happy mapping!