The rear of the device is home to its one and only button, usually serving to answer and drop calls, but also giving access to a couple of other features with differing press-and-hold combinations. Holding the talk button and turning on the Jawbone, for example, places it into pairing mode. It's worth mentioning that with my iPhone 3G a second battery indicator appeared on the iPhone's status bar, showing the Icon's charge level. I can only assume other handsets could have similar functionality added in the future.
Because you can't - or at least shouldn't - be looking at your phone's screen when driving, the Icon also has voice prompts delivering useful information. These range from spoken warnings about battery level, to identification of incoming caller ID. There's also support for voice activated dialling, as long as your phone is compatible.
The inside of the Icon also features the trademark Jawbone Voice Activity Sensor (VAS), the base of which is circled by a status LED. The VAS cleverly lets the Icon pick up vibrations from your jaw when talking, adding to the noise-cancellation accuracy of the "NoiseAssassin 2.5" system that purportedly improves upon the already impressive previous Jawbone headsets. Also helping make calls as clear as possible is "Wind-Noise Reduction Technology", which claims to do just that in gusty environments.
The in-call results speak for themselves. Only because the others could see me in my car were they able to tell I was in it - engine noise was completely nullified. Upon venturing into a busy main road I had to open my windows before the traffic intruded into my conversation and even then external noise didn't impede it.