I downloaded and installed Salling Clicker on my treo last night, and i have ot say i'm pretty impressed with it.
What is does is connect bluetooth to your computer, and you can control apps. Think of it like a remote. You can control itunes, front row, iphoto, move the mouse around with the stylus... it's really neat.
It works on a ton of bluetooth phones, not just treo's. see the list here:
http://www.salling.com/Clicker/mac/devices.php and download the app here:
http://www.versiontracker.com/dyn/moreinfo/macosx/18500