Well, you could always point a video camera at the screen, and connect that to a TV...

The speakers on the N800, at least, aren't bad at all. I have found a trick to get even higher volume out (speakers or headphones), but it's quite respectable without.

The screen is viewable from quite a wide range with no color flips or anything, but it's a 4" screen. I guess how many people can watch depends on their eyesight...

(Honestly, they sell fresnel lenses (or did ~3 years ago, I saw them then) to place in front of a monitor and use it as a projector. I think a fairly dark room would be required, but that's possible.)