If you're rooted, get the flashable zip file to integrate it into the ROM from their website (under download section). If someone does a factory reset on your device, Cerberus remains installed
there are a few cons with programs like this.
1 it murders your battery
2 your phone will just be flashed and ready to use again.
the chances of getting it back are slim. but a app like this is all you can do to try and get it back.
1. Wrong. Cerberus has never drained my battery. Unless of course you sit there tracking it for hours through the web panel
2. It's highly unlikely that the thief will know how to flash a new custom rom. Most they'd probably try is a factory reset, which wouldn't touch Cerberus if you've installed it as a system app.