that is true... they just found this family's dog in somewhere like montana after it wandered off 4 years ago... it went over 1100 miles. the dog had a little GPS chip and the vet used it to locate the owners. here's another story: http://www.ocregister.com/ocregister/homepage/abox/article_1727207.php
You have nothing to worry about... He's not paid in full yet. He still has almost 2 months to find an excuse to back out
I'm thinking more along the line of nanotechnology. Like very tiny unnoticeable device (think the movie Innerspace). If I put a dog collar on her, she can just take it off.