There's also a new lightweight app under development by no2chem on xda:
http://forum.xda-developers.com/showthread.php?t=459604
it allows you to send text message with a command and your pin (defaulted to 0000 but changable in registry), it replies with a gps position on next location, a link to google maps, and soon a feature that allows you to send a command which will make it set your ringer to high volume and set off an alarm (in case you lost your phone nearby)... Personally, I love it!