You can't prevent theft with a gps tracker, you can only improve your chances of recovering your bike, which is cool I guess.
Of course you need to physically confront the thief and reclaim the bike, no issue if you're a hard bastard and he's a pussy, might be a different story though if he's a knife wielding zero fucks giving psychopath who lives in the middle of the roughest estate in moss side.
Personally I never leave a bike I want to keep unattended, I have a shitty but rideable rat bike specifically for those occasions when I know I'm going to have to leave it locked up where Africans are likely to be.
