My silence hasn't been an indication of inactivity, I promise. :)

I've put a ton of work into the back-end REST interface that serves the mobile app I'm developing for Fursquare. GCM push notifications now work like a champ, as well as forming group chats, inviting users to group chats, messaging, muting (silencing notifications for a group chat for a period of time), and leaving chats.

This is a quick screenshot of what the notifications look like when the app receives them in the Android notification tray