Ok, guys since it is now possible to actually do interesting stuff I will just build the adapter as a purely mechanical design - pair it with a Sparkfun level converter (
Sparkfun Shop Link).
Its not like i could beat that 1.95 USD price point anyway. I will post the board design and do a few PCBs + do the postcard thing if there is any interest.
UPDATE: the sparkfun level converter seems not to work with the kindle - my bus pirate + short cable worked tho