One critical feature would be local storage of recorded video. It would be a huge invasion of privacy to pull images from innocent people, even if it is for the greater good, maybe. I don't know which side of the privacy debate I'm on. If there is unlimited transparency for citizens then there should be 100% transparency for the government, that's the only way.

The 3D mapping thing has already been done. http://arxiv.org/pdf/1209.5982v1.pdf