Wireless Mouse thats a pen
Check out this wireless computer mouse that is also a writing pen. Detach the receiver and attach it to your PC via a USB port. When you are finished reinsert the receiver back into the pen and power will be turned off automatically.

 
 
If you select pen mode and change mouse registration information, you can use Pen & Mouse as a real pen to write, draw or sign. Compatible with Windows 2000, XP, Vista or MAC OS.Via Aving & Pen & Mouse

Cool!