BBM-type android service
You've described Huddle[1], part of the Google+ app for Android.
"Huddle lets you send super-fast messages to the people you care about most."
Presumably, Huddle will be part of the Google+ app on other platforms, too.
[1] https://market.android.com/details?id=com.google.android.app...
edit; If they created some kind of BBM-type android service that sat on top of Google+ I think it would make me switch my SMS usage because I have a lot of friends that use Android phones...