Lua was the first language I learned, and I can say with all honesty, it's best application is math. For drawing images and then the Gu functions it is very slow (dependent on how it's been programmed of course). As Link said, theres already a small library for lua on the Wii, although it only has very few functions, and once it has enough functions to create games (if ever) they will likely be very different to the functions on PSP, so it wouldn't be able to run straight as is, although possibly with some tweaking you could. But short answer is it can be done, chances are it won't be done the same as PSP and if it is, it will be a long time in the future.