Here's something I hadn't thought of: using a bluetooth headset with iChat. I already use iChat a great deal for communicating remotely with coworkers, but I usually wear big stereo headphones and use the iSight as the mic. Instead I could be wirelessly talking and listening using something like this.
I always knew iChat coupled with an iSight was a killer combo and I greatly prefer it over regular conference calls, but with a bluetooth headset it becomes even more useful for one-on-one conversations between other people with the same setup. Heck, if everyone you knew had a powerbook, iSight, and a bluetooth headset, this would kick ass all over Voice Over IP systems.