A microchip is an inexpensive, non-injurious way to make sure your quadruped friend gets home if s/he ever turns up in a shelter or a strange vet's office.
For those of us who would not bat an eye at borrowing money to recover a missing small animal: You can get a transmitter, small and light enough to be comfortable for a cat to wear on the collar, and a receiver for a few hundred dollars. One kind of receiver lets you carry it and gives you more frequent beeps the closer you get to the transmitter. Another kind may not be possible to carry but has a screen showing the transmitter's location and its path for the past
X minutes; this is useful because straight lines with right angles show that the animal is in a moving vehicle. If a small animal gets lost, the best single resource i've seen in 15 years of animal rescue is lostapet.org.