An AP story in the Washington Post reminded me of the importance of microchipping pets. Basically, a dog was stolen in Florida (another reason to always supervise outdoor playtime, sadly stealing animals seems to be getting more common) and turned up several months later in Illinois when his shoulder was checked for his microchip.
Microchips are not gps systems that tell you exactly where your pet is. However, almost every shelter and vet in the country automatically scans strays to see if they have a microchip. The information (like a barcode on a product at the store) ties into a database and brings up the information the owner chose to include. Most of the time this includes the last rabies vaccine (this can save your pet because if an animal might have rabies, many counties require putting him to sleep to avoid infecting others), allergies and other health issues, contact information for the owner, and the pet's name.
Most vet offices will put the microchip in for you, but many shelters are doing this now, too. It costs $30 at the shelter I used, $90 at my friend's vet's office. The animal might be uncomfortable, but more from being in a medical environment than having the chip put in. It's shot just under the epidermis, usually by the shoulder. Toby meowed a bit and fussed when he was chipped, but he was freaking out more because it was a shelter with dogs barking than because of the procedure. The procedure itself took only a few seconds and then I filled out some paperwork so they could upload my information into the database. I now can change and update Toby's information as needed (such as with my new address and his most recent rabies shot) so that if he were to ever escape he wouldn't be in danger from being put down for rabies fears or simply due to shelter overcrowding. If he was found, the shelter would scan him, call me, and hold him until I could pick him up.
We will never be able to 100% prevent our pets from getting loose, but we can make it a little bit easier for them to find their way home.