Nano-X (aka Microwindows)

[Crimbo]

Mills on the comments pointed out http://www.microwindows.org ...stating that there's a video online showing it running on the PSP purely to run a minefinder game.

This might be useful as it is Open Source and offers to bring a graphical windowing system to a majority of systems.

Nano-X does not require any operating system or other graphics system support, as it writes directly to the display hardware.