There is already one for the PC that emu's the PSP but it is slowwwwwww as hell, if you want it you can grab the build here...

http://jpcsp.googlecode.com


As for the PS2 emu, no it wouldn't be possible on a PSP but a PS3 yes as it requires around 10x as much power to emulate, possibly PC it would work but NOT PSP.