If a printer doesn't need toner, ink or copy paper, is it still a printer? Well, I guess if a bear still shits in a forest, then yes. Using plastic paper, it's a very green (and pricey) way of printing.
The PrePeat RP-3100 paper is actually made from PET plastic, which means it can be reused up to 1000 - so once your printed document is no longer needed, it can be inserted back in the printer, where the line thermal head prints the ink-less words on again.
However eco-friendly it may be, there are some major downsides to the PrePeat RP-3100. It only prints in black and white, and costs a whopping $US5600 - which each sheet of plastic paper costing a further $US3.35. Each. I guess you don't need to buy ink for it, but that $US3.35 price does sound astonishingly high. [Sanwa Newtec via Crunchgear]