There are some similar things out there that are smaller. I have the info on my other computer and will post it tomorrow. I forget which one it is that's small enough for a yorkie, but I"ve researched them and I know there's one at least. I think if you do a search for gps units for pets, you'll find a lot of different options.
One thing though, is that if you're dog is stolen, thieves would most likely remove the collar anyway. What they need to come out with is a microchip that has gps capabilities!
Even if thieves did remove the collar, at least you might have an indication of which way they started off.....and be able to possibly retrieve the collar with fingerprints??? I know...I watch too much CSI
.