Another option that might work is LowJack. I'm not sure of the details, as I haven't looked into it though:
We had a laptop stolen a couple of months ago. The owner had a Lowjack system installed on it. When the item was (when an item is...) reported stolen, the stolen status will make a signal go out to activate the Lowjack as a beacon. Patrol cars have a series of antennas on their cars that can help locate where the signal is coming from. We found the stolen laptop a few hours later in the possession of someone...
I think OnStar has a small transmitter too. Motorola phones have a locating device in them, so when it's activated, they can locate where you are to within a few feet with a GPS signal. We had a woman go missing for several days and they checked her Motorola GPS signal and found her within a few hours upside down in a gulch. As I'm not up on electrical engineering, I don't know if there is an independent power requirement on these devices. They are obviously small and getting smaller. I think that within a few years, you'll likely be able to get something the size of a quarter and put it in a systainer to track it down.
They already have radiofrequency diodes that cost about a penny and can be sewn into the fabric of a shirt. When the shirts go into a store's inventory, they can tell how many of what size and style just by scanning the RF diodes. They can also track consumers that come back into the store at a later date by registering the RF Diodes at the entrance (kind of like Cookies on your computer!).
One of the biggest ways to make items identifiable and to possibly get them back.... Record your tools with their serial numbers and with photographs. You would be amazed at the number of people that don't even record this information. They will have a garage full of tools stolen and not even have the serial number for their $500 SCMS! A second major deterent is to inscribe (not just paint) an identifiable number into your tool. Here in Washington, it's recommended that you inscribe your driver's license number. Any pawnshop owner will have second thoughts about taking something that is inscribed. If the inscription is filed or rubbed out, then that will also cause some angst or trepidation.
Rod