From what I gather, if you need fine-grained location information in a building, you can do this without cameras and just a handful of strategically placed wireless access points.

Less likely to be seen as creepy and such systems already exist.

If you just need 'is a person in this room' or 'how many people are in this room' levels of data, solutions to this problem have existed for decades. No need to over complicate a solved problem.