Why not just tape a business card or stick an address label to your stuff with your phone number? Add "reward if found" if you think it is necessary, but I don't see why you need a third party to manage this for a fee. Honest people will honor this, while dishonest people will keep your stuff no matter what the label says.

The only electronic gadget I have lost (beyond the cost of a phone charger) is my cell phone, on the golf course, 10 years ago. The guy that found it called my home number and left a message, and I arranged to pick it up from his office the next morning. I did similar when I found an endorsed check on the ground at the ATM late one night. Since the bank was closed and the address of the person that wrote it was only a couple blocks away, I dropped it in their mailbox with a note that it was found on the ground at the bank.