I share your enthusiasm after all how is a 100 dollar printer a money saver if you need a 1000 dollar computer to run it!
I think the quickest and most likely candidates for what you suggest are the newest Rpi and perhaps a beagle bone

running from source on a GNU system is rather easy.

Another option that we want to explore is an sd card add on, you would use your computer and the peachy software to export your print to the sd card
then plug the sd card into an addon board that fits on any v1 printer. Then the printer could finish a print without your computer, it would just need 5 volts from a usb charger.
There are plans to develop this some day.