"Touch Diamond owners will know that the navi-wheel on the front of the device is capacitive, and can measure movement without actually rotating.  Like many HTC devices, it seems the Touch Diamond and Pro have hidden features, and pretty tasty ones indeed.  Using an application called Nav Debug Tool by HTC, this video shows not only is the navi-wheel capacitive, but that the whole front of the device can track finger movements, and even two fingers independently.So far there is no know feature on the Touch Diamond/ Pro that exploits this, but once our developers get their hands on the API it wont be too long. This also promises that even current generation devices with resistive screens will be able to take advantage of multi-touch features in WM7." via wmpoweruser.com