This thin and flat little number from Brother only prints on post-card sized A6 paper, but in addition to the USB connection, you can print without wires thanks to the integrated Bluetooth and Infrared support. According to Akihabara News, the MW-260 weighs about a pound and measures in at a small 160x210x18.5mm. The pint-sized printer supports printing from a Windows PC or a Windows Mobile 2003 or better handheld device.
Since the product page is in Japanese, I’m not seeing if the unit has a rechargeable battery for full portability or not, and I also see something about printing from a BREW-capable phone; at least that’s what it looks like. We’ll know for sure in March of 2007 when the product expects to launch.