Thousands of dogs caged / slaugthered / eaten every single day in the middle kingdom... maybe you shouldn't buy a "bread" dog. Better help one out and find a loyal friend for live by adopting one of many! If that's an option for you, get in touch with Robin aka mPRin (use search function on top) and visit a dog shelter.
I agree with you and must admit 150 RMB is not a bad pricetag, since reliable GPS trackers cost a lot more + SIM-card and additional cost. I lost four bikes over the years and will probably give it a try.
@Geezer: The funny thing is, the GPS thingy isn't battery-powered. My first thought was like yours, they just cut the power and the signal is gone. My neighbour showed me his plate and it looks like a normal one... just bigger than the old plates for ebikes.
@Dazzer: They will also engrave the plate-number on the bike-frame like with the normal registration/plates you could do before.