Got a shark helmet with Sharktooth headset, awesome but of kit, section in the back of the helmet so is the slimmest of all as only the controls are in side of helmet
iPhone (music and siri, so pretty much everything iPhone as so.... send text messages, directions, GPs etc and can pair a full on GPS if needed.
Use it every day on the highway commute, makes me ride even faster sometimes, got a few issues so my brain is always doing a million things at once, then there is two of us, so twice as many thoughts can be processed