The soon to be released ZeptoPad 2.0 will let you doodle on TV/projector screens, etc. via your Mac or PCs.
No jailbreak necessary, you will just need to know how to connect your Mac/PC to TV/projector.
I will let the developer reveal the secret themselves later on when they release it; i heard it'll be sometime next week.
They made a video for it:
Diddle on wall with iPhone from Ryo Shimizu on Vimeo.
They just made another one, but I like the first one: