Turns out that it's probably possible, using http://code.google.com/p/python-on-a-chip/ . Now I have new questions:
* Has anyone tried running e.g. python-on-a-chip on a Teensy++?
* If so, what's the speed like?
* Also, is support for the fancy peripherals included, or would I have to add bits and pieces of C to do that?
[edited for readability]