There have been a few threads on MCM about GPS trackers. It is always interesting to see which are the latest products that are hitting the market.

I've several GPS trackers of various shapes/sizes/features, acquired over the years, and here are my thoughts:

1) They are trickle drains on motorcycle batteries. You need to ride at least once a week to keep the battery charged;
2) Units with backup batteries are good, especially since they have some nice features (it will sms you if the power is cut, or even if your battery is getting drained to a low level);
3) They are all great for recording tracks of where you have ridden;
4) They are cheap, so if you believe that a pro thief will find/cut power to your Tracker, install two - one acting as an "obvious" sacrificial tracker (probably the one with direct power, wired to the battery), and one with a built-in back-up battery (oops, I am giving away one of my secrets on a public board!);
5) They are NOT theft-protection, or theft-deterrent, devices. They are hidden, after all, and only worthwhile for potential recovery;
6) If your bike doesn't have an ignition key chip, you may want to install the GPS tracker that includes an immobilizer. Several thefts (I don't know if it is "most") happen by cracking the ignition lock (which is surprisingly easy). I would guess that at least an equal number of thefts happen by van-hops (even easier, IMHO, and very fast); and,
7) Thefts can happen anywhere, any time, in the blink of an eye ... plan ahead as to what you will do if your bike is stolen and you are tracking it. Personally, I subscribe to the "call the cops" theory - taking matters into your own hands (although tremendously tempting) can have dire consequences, especially in China.

If you want theft-protection, or theft-deterrence, consider:

1) NOT BUYING ILLEGAL BIKES! You are supporting the thieves. Supply/demand equation;
2) Chain the bike to something secure or, if nothing is secure, chain it to another bike - lifting two bikes into a van, at the same time, is near impossible.
3) Use several methods - chain, disc locks, cover, alarm, etc;
4) Not very neighborly, but try to make your bike much less attractive/available than someone else's;
5) Park it in a way that requires the bike to be wiggled and shuffled through a 10 point turn, to get it out;
6) If you have the bucks, get an alarm that will play a recording. I saw a demo of an alarm that would continuously play, in a screaming female Chinese voice "Help, Help, I am being raped! HELP! HELP!" That really got people's attention - more than the typical alarm which everyone has become immune to and simply ignores. This particular alarm was large and meant for a car, but there are probably smaller ones that could probably be hooked up inside a bike; and,
7) Rare for this to be possible in largely-condo-living in China, but a big dog is ALWAYS the best security. As a consolation, however, there is that "mob-justice" inside China that is quickly inflicted on thieves caught in action.