I always thought it would be sweet to have a whole house camera to see inside your walls. Knowing where all your pipes are, knowing where voids are, maybe detecting leaks inside your walls, animal/rodent detection, etc. Antenna arrays in GHz bands should be able to have pretty good resolution on metallic reflectors. I guess add intruder detection too. If our privacy is being violated outside our homes, I'd at least like to leverage for some good inside my home.