GPS bike tracking (locks) I have seen a few GPS devices either in the backlight or unside the seat tube which you can track if you lose your bike (your bike gets stolen). 

What do you think about this stuff. Is it worth the money and how easy is it to track your bike with this things.
Pain in the ass, and waste of money.

As of the last time I checked, you can't track them directly (there'd be no way for you to receive a signal from a battery-operated device 5mi away), so you need to sign up for a recurring monthly service. On top of that, they chew through battery pretty quickly, requiring a recharge every few days.

Contrast that to just buying a decent set of locks. If you need to lock up your bike in the same place every day, get a thick $80 chain and a cable for the front wheel. If you need something lightweight to carry around you, a $50 u-lock is going to be a reasonable level of protection.

If your bike is worth more than a few grand, you're absolutely crazy to leave it outside at all.