Think about it, if you were to stretch that screen on the handset when and only if, plugged into the TV set, it would look hacky and awful at worst!
Reasons include:
- Would chew up a lot of memory to allow translation on the fly to accomodate the width of Android's graphics frame-buffer device - which is a limited size based on the resolution of the handset and only one framebuffer is available!
- An extra layer of complexity to tell Android "Right, we're plugged into TV, now stretch"
- As RAM is chewed up to "accomodate" a bigger buffer to hold the graphics in a stretched state for desktop screen/TV, that could result in Android slowing down to a crawl as the apps would not have enough RAM available to run in.
All in all, it may be do-able, but having to reserve memory for the "stretched" resolution, say, for example, 800x480 resolution, Portrait mode on WVGA, 480x800, Landscape mode, 800x480, using that one singular frame-buffer device.
Have a mosey around in the kernel configuration as there may be something in there for Media/TV capture...? as for the actual app within Android itself, have not seen it. Worthy a investigation into the kernel though :)
But then again, if there's a chip that supports HDMI, maybe its a different story, but interesting question OP! +1 from me!