Yeah, that's a nice idea. At least if you're doing instrumentation tests.
I have seen this done already with vnc2flv. Normally I run my emulators inside Xvnc (as described on the wiki), so you could capture the VNC output directly.
However, it would be nicer to capture only the actual emulator screen, rather than an entire Xvnc desktop.
I have vaguely noticed that the Android emulator/qemu itself has some sort of in-built VNC support, so maybe it is possible.
Do you have any further info about how this could be implemented?