We had all of our cats microchipped with HomeAlone chips - this is what they use on the military bases and also at our local veterinarian. I don't know anything about the other companies - but HomeAlone has a nice website where I can easily go and update anything in a couple minutes. I even have uploaded pictures of each kitty and little plastic ID tags to keep on my keyring. Since they are indoor only, I never really gave it much thought until reading about Kuhio and then the Katrina mess and figured it may or may not help me find my pets again if anything disastrous should happen where I live - but worth doing anyway. They do not wear collars at all so I feel better knowing that they have the chip. I am curious about the local shelters and will give them a call to see if they have scanners and routinely use them. I am one who thought it was very common these days Better than NOT having anything on them though.