HP Pocket Whiteboard
HP recently announced the HP Digital Learning Suite.
One item mentioned, as a component of this suite, is the HP Pocket Whiteboard.
It consists of a receiver and wireless stylus and allows almost any flat surface to become a digital whiteboard (I'm not sure it will work on glass).
The receiver is connected to a PC using a USB cable and captures strokes and taps using the stylus which are recorded and can be processed by software.
It's scheduled to be available by the end of February 2011 - I haven't come across any pricing information yet.