I was asked by a potential client if I can have my software interact with Esri/ArcGIS Online.
Use case: users is logged into SomeRandomSoftwareApp and is looking at a Widget, this Widget includes an Esri asset id, the user clicks a link that passes that ID to Esri/ArcGIS Online and behind the scenes the user is logged into Esri and they see the data associated with the Esri/ArcGIS Online.
Thanks, Keith