I learned about the Smart pen a while ago and it looks like they are going to or are in the process of making a application store much like the one for the iPhone, there is one application that is native to the pen that plays a piano that is drawn on a sheet of paper. I think it would be really great to be able to draw out the knobs and buttons for a synthesizer and play it on the page, or do something like the kaoss pad that I brought in last meeting.
I also think that it would be beneficial to be able to use external microphones of a high-quality nature instead of the one that is on the pen, it would be great to be able to use something like Bluetooth to get that done. I do not think that they will open up the hardware, but perhaps they would be open to a proposition from a developer, but that is water that I have not tried it before and perhaps it's something to try out the future.
I also think that it would be really cool to be able to wirelessly send MIDI data or open OSC data from the pan to a computer.