Cerberus can be activated by both it's web service and via text message. If you're rooted, it can be integrated into the system apps and so survive a complete wipe. FYI, NO app will let you track your phone while it's turned off :)
It can also turn on the GPS remotely, has real time tracking using Google maps (looks like Google navigation in a web browser), take pics/record sound & video, sound an alarm, hide itself from the app drawer so thieves won't know it's there, remotely lock the phone with a code, wipe the system, display messages, download the last 10 texts and phone calls, and LOTS more.
Cerberus is $5, and worth every penny. It can be downloaded from Google Play, but the download section on the official site has Cerberus APKs that can be flashed and integrated directly into the ROM.