I applaud sonos for enabling the URL scheme to allow the an app (such a an home automation app) to launch the sonos app, but this is only have the job. Can we now also have a "return to originating app" button added to the sonos controller. Its possible at least in IOS as CasaTunes has this included in their controller.
here's a link describing this with Roomie Remote and casaTunes
http://www.casatunes.com/multi-room-audio/index.php/product-tour/roomie/
quote
"Simply add a Roomie Activity for listening to your CasaTunes music, add a Roomie Command of type URL, and configure the URL to launch the CasaTunes App when pressed. When launched, the CasaTunes App will display a back button with an optional custom label you supply, which when pressed will return control back to your Roomie Remote App. "
here's a link describing the back button for roomie
and for ON Controls..has a picture of the back button
http://www.casatunes.com/multi-room-audio/index.php/tech-docs/oncontrols-1/