I have never used this service, but just this morning we received an automated call from them about one of our neighbor's dogs.  Honestly, I had never heard of this service before Robert used them when Louis was missing.  He seemed to be happy with the service.  Perhaps he will comment in more detail.

The prices are listed on the website, and they are a bit pricey.  But I guess you would have to weigh the cost against the difficulty you are having finding your lost pet.  It's a good option to keep in mind should you ever need it.   
The website is http://www.findtoto.com/.