This is a paid service like the above. The finder puts the key in the mail box, and they get shipped back to you.
http://www.keythings.com/
Or Maybe you could try these services:
http://www.keyreturn.com/ (this says its a free service)
http://www.key-rescue.com/ http://finderproducts.com/products_keyfinder.htm http://tracertags.com/html/tracer_tags.html#key
I use the following:
www.buddytags.com
phone number: 720-249-2575 (USA)
You get a tan metal tag, that has an 800 number that the finder calls. BuddyTags.com them calls you or emails you to let you know where your keys are at. It cost like $9.00 USD.
I hope these help
Nic