Build an Android Client
Build a client for android that interacts with the GPS and lets me get back basic user information (Like iEngage for the iPhone http://code.google.com/p/iengage/)
There is an open source project started by Emidio Picariello ! see it at smslocation.googlecode.com
I also started one here:
Sorry, I didn't know about the other one. The one I'm doing lets you see the groups you belong to, the users you know, the messages you received... and that's it so far, but you'll be able to see users' locations, groups' locations, send messages, etc.