seems that you are on the right path, even though the output of your phone is HDMI (wired or wireless) and the TV screen is lousy 640 x whatever... which i don't know if a way to improve that as the video is gone through the TV module and can't be "enhanced"... so, it will be crappy...

as far as motion unlock - i use a hardware microcontroller for the unlock, that gives me two features - it allows me to turn the TV-in-motion ON and OFF (i guess for law enforcement or technical inspection pass) and also allows to pass an alternative sound source... without the hardware you might only have the mono... i am not sure about this one...

on your Nexus picture i spy an additional device next to TV, probably the actual receiver... does it have to have a stand alone wifi router? the HTC uses a router too but in absence of one, connects directly to the gadget...

i'd like to see your execution of this as well as any other possible solutions... keep us posted...