Can one create custom widgets in Web AppBuilder/ArcGIS Online?

[JayHodny]

I think I know the answer, but I want to ask the question.  I would like to create/add a simple custom widget to my AGOL hosted app, or make use of an existing WAB/AGOL widget, to display available parking spaces in a text string in real time.  The map and app were created using the Public Parking LG Pro solution and the AGOL WAB, not the WAB Developer edition.  We have figured out how to retrieve the space count from our parking vendor.  Currently we are displaying the count in real time in a feature service on the web map and app (see screen shot of the app).  We would like to display the count in a text string either in the opening app splash screen, or better, in an 'Information' widget that pops open on app start up (see example screen shot).  I don't have much experience in using the Developer edition, so I am hoping for a way to do this in the AGOL hosted environment.  Many thanks in advance for any help and ideas.

[RobertScheitlin__GISP · Accepted solution]

Jay,

  As you probably expected custom widgets require WAB Dev or a locally hosted Portal. You can not accomplish what you are after and have the app hosted on AGOL.