Briefly, the locater on my laptop tries to upload a current location every 15 minutes. It looks to IP Chicken to check out my external IP address and tests this against a file with a list of known IP addresses and names I've given them. It then uploads a small text file to sollaires.net that a PHP looks at and uses to write out the current location.
If my laptop hasn't checked in in over 15 minutes, that means that it doesn't have a connection at that moment. Which really means that I either don't have a connection or that my laptop is sleeping or off. Neat.