I'm a big fan of the Jawbone Icon. It seems in this model, they worked on the issues they had with hiding buttons by trying to be so sleek and cool. Now it's much simpler, and there are is an optional earhook and several earbud cushion sizes and designs to make it fit better. It comes in six designs (shown here is the model I tested, named "The Ace") and costs $99.99. It speaks updates in your ear for caller ID and battery life, has up to 4.5 hours of talk time and 10 days of standby time.
It connects to multiple cellphones, and iPhone users can see a battery meter on the iPhone screen.
The volume was great on my end, and callers reported hearing me loud and clear -- it was hard for them to even tell I was using an headset. But I hate how they made the charger cord two inches long, so if you use a wall outlet or power strip, it just dangles there.
Bottom line: Works and fits like a dream. Soon the company will be launching extra apps for Icon (currently in public Beta testing) that let you convert your speech to text messages, call using voice commands, and change the computer's voice to be more sexy. Hey, if you're paying $100, might as well get a little fun out of it.