There are a few solutions for Pocket PC (
dotpocket) and Palm (
see here.
For PSP there's
PSPonTV.
For Nintendo DS there have been various
rumours but nothing concrete.
I'm afraid neither the PSP or DS solutions are that great.
OO I got excited reading this! I have used Margi Presenter to Go (in my drawer gathering dust now) and a PPC in the past with a dismal display and such fiddle to get it work properly so I'm quite keen on playing with PSPonTV - so thanks for the idea.
However, the PSPonTV website offers the view that families will watch projected games. I would have thought it better to use a Playstation to link to the TV if gaming is the aim. I have several PSP films (on UMD) and I doubt if a projection to a large screen would improve the poor image I've experienced.
If it's for web surfing as a group then I would imagine a projection could be useful but I would always opt for a laptop/projector for good connectivity, ease of navigation amd much more versatile. I'm still getting to grips with the little joystick (or whatever it's called) on the PSP that allows you to move anywhere.