This has been discussed before. If a real thief steals the tablet, he will instantly reflash it. However, if it is just a casual one, I think a better solution would be a homebrew one.

First of all, we should use the new GeoLoaction WiFi API's or something to get an accurate position. The tablet can update this when it has a WiFi connection. It stores it on internal memory, and when queried, it relays it to the remote user. This way you can even track where it went! Also, we should utilize the camera, and stuff.