I know a tv can send back commands from e.g. the remote control over HDMI, it really is bidirectional communication, but I wouldn't know whether it's good enough for something like touchscreen.
Well you can do 100Mbps Ethernet over HDMI 1.4 with a compatible cable, so I don't see why it would be technically impossible. The question is, can this stick do it?
No. Touch screen monitors with HDMI need another channel, usually a USB port, to send touch events. In theory, I guess you could send events over DDC, but then you're gonna have to get video driver makers involved, make sure that the spec you choose doesn't cause existing drivers to puke, etc.
