For my Jawbone II is use a custom molded earpiece from www.averysound.com. These are expensive at about $60, but will absolutely hold the bluetooth for which they have been designed. Don't use this cycling, however. One the tandem we use Blueant F4 Interphones as both an intercom and cell phone headset. No self-respecting roadie would be caught dead with the Interphones, however. You'll need something like a Jawbone that has it's microphone enable by vibration. Otherwise the wind noise will be beyond brutal when you're actually using the cell phone.