The pocket-sized PrintBrush is claimed to be "the smallest printer device in the world that can print full size formats -- at 600 dpi and uses Bluetooth and rechargeable batteries to print without any wires whatsoever." Available in 2010, priced at $199. Video after the break.
The real beauty of the PrintBrush is that it'll print on any flat surface you like, meaning that you can print addresses directly onto letters, for example. It even prints on fabric.[via OhGizmo - PrintDreams]
