I have a "universal earbud" for my phone that I use while playing Quake3. We all get on the phone for matches (great voice comm makes a <b>huge</b> difference). I have the earbud in my left ear, microphone on my shirt, and then headphones over my ears. It works *really* well.
Before I had the earbud, I would just put the phone under my headphones and kinda hold it with my shoulder. It worked really well
I can't say I've ever rubberbanded a phone onto my head though