Alright, this is not just concept. PrintBrush is a real product, wirelessly connected via Bluetooth, powered by rechargeable batteries and print on any flat surface even fabric. It uses some super accurate optical sensor to detect and can print a full size A4 or letter format silently. Expected to be sold in 2010 at $199. Video after the break.
World’s Smallest Printer Device – PrintBrush
Alright, this is not just concept. PrintBrush is a real product, wirelessly connected via 
