I think privacy ought to be another huge concern. Think about it: You will have a camera and a GPS monitoring your every move. If that information gets into the wrong hands, it could be disastrous. I bet some developers may try to sneak in some data collection so they can sell it and make money off of the app. Google will really need to crack down on reviewing apps, and ensure they cannot do bad stuff.

EDIT: I guess I wasn't clear in my wording, and not entirely accurate in my research. According to what I've seen in the API Docs, 3rd party apps will not have direct access to the camera (but might be able to access saved pictures), but they will have access to the last known location (so yes, it's about the same access level as a smartphone). Also, I have little concern over Google's collection of data (they've been doing it for all the services for years, apparently ethically), but am more worried about the 3rd party devs, who may rely on sold data as their only source of revenue in-app.