What would be your dream PSP homebrew app that's within the realm of possibility?
High ups for me would be...
Quake 3 Port with or w/o Infrastructure Support - possible since the open source code has been released and the settings can always be toned down. The bots and fast paced action make it one of my favorite games ever.
A full functional operating system like Windows XP that comes with programs like an internet browser and something like Word. - Totally possible since that one coder already found a way to run Windows 95 on the PSP at a decent speed.
But the winner would be...
A full functional N64 emulator that uses Infrastructure to let up to 4 people play against each other online - doesn't have to run at full speed, just a playable speed. It would take quite a bit of coding to trick the system into treating other players online as just 3 additional controllers and trasmitting their screens to them. But damn would it be worth it. Perfect Dark and Smash Bros online, can you imagine?
There are so many kick @$$ games on the N64, Perfect Dark (the 2nd best FPS even today IMO), Conker, Goldeneye, Star Fox, Mario RPG, Zelda, Smash Bros, Battletanx, Starcraft (I love RTS and the thought of playing the best one ever on the go is a dream come true.) and dozens of others.
I think this is also very possible with some extraordinary coding since the psx has been emulated (though not well) and the psp is much more powerful than the N64.