both Belle and Bear are chipped, they were chipped when they got fixed. Rudi will get chipped then too, but I'm thinking on waiting awhile to get Rudi fixed so I might ask them about it when she gets some shots next Wednesday...
The chip readers can read any kind of chip, the only difference is where each chip is from. even if the chip isn't registered, you can still find out where the chip was implanted and most likely the vet knows where the dog came from. that happened to us, a woman across the street found a husky running around and asked if we thought she had a chip. we said we didn't know, but the woman took her to a nearby vet and got her checked, she had one, and then she told us the chip number and we looked it up on like avid.com and it siad which vet she was from because she wasn't registered, we called the vet and they knew exactly which dog she was! She gave us the address and she was taken home immediately.
I think they are a very good idea. I wouldn't invest in a GPS collar personally because if can be removed, and my dogs are not usually out of my sight anyways so a GPS wouldn't make much sense to me. If they start implanting GPS into a dog, now that I might look into.... lol.