Dahua has Intelligent Video Surveillance (IVS), I have a pair of cams with such features on there way and a NVR that supports being triggered by them.. I hear the facial detection and people counting work well but I dont think you can have multiple analytics working at the same time... ie, its only looking for faces or missing objects, not both.
Both of the cameras I have coming were under $200 each, 4MP.. if they work well I have a couple more cameras i'd like to get.
I believe some Hikvision cameras have similar features for the same price point.. the only analytics I have not seen on any affordable cameras is ALPR, those are still in the >$500 range.