I know what you're talking about.
Zelda Classic is a PC version of the classic NES game The Legend of Zelda. There is also a program which allows anyone to create their own quest to be played in Zelda Classic, including the overworld, and the dungeons, and everything. If ZeldaClassic were ported to PSP, anyone could create their own quest on their PC and put it on their PSP or just pick one of the many quests available on ZeldaClassic.com, and there would always be something to do.
I've been thinking about this a lot, and I would love if someone could do it.