In view of the fact that some of the gps monitors don't have the kinks worked out of them yet, microchipping is best, and the collar with name and number embossed on it is second best. The only problem I see with that is many cats and some dogs will not respond to strangers.So hard to get the animal close enough to catch and have chip read, or catch and read collar. But it's better than nothing. Check this out
Amazon.com : Custom Embroidered Dog Collars - Personalized ID Collars with Pet Name and Phone Number. Adjustable Sizes with Plastic Snap Closure. : Pet Collars : Pet Supplies
I have had so many of my dogs' tags come off while playing,that I think the collar with name and number is an excellent idea.--second line of defense beyond microchipping. And sometimes I wonder if it would get you your pet back faster since all someone would have to do is pick up the phone, as opposed to taking the pet to a vet.