Colin, us (TechnoAware) we can actually offer video analysis functions for detecting those events: functions Loitering, OccupancyRate, PanicDisorder in particoular.
Nevertheless, I fully agree with John about the complexity of those behaviour analysis, above all in crowded areas. All depends on the complexity of the scenario. To have for example an efficient loitering detection (read long term tracking of a subject..) among a crowded area is, at today, still too challenging to have useful results.. (Even if I remember to have seen more than "someone" claiming its fully compliance in some absurd tenders (above all from Middle East) requiring multi-camera tracking among crowd.....;))..)..
On the contrary, for example, a group formation might be anyway easier to detect. While a panic/aggressive behaviour could be easier to detect in a place where people may be even a lot, but reasonably behaving with a regular dynamic: inside a stadium, for example, it may have no sense; but outside the stadium maybe yes..
As John wrote, "Whatever you look at, please thoroughly test.".
Thus, more than just claiming, as we usually do what we can offer to you is a free demo and all our technical support to test it directly in "your" scenario. Or, do you have videos from that scenario that we can try to process together offline to see what happens? Then, let's see in real life if we can achieve useful results or not.. Please, feel free to contact me for that.
About the price; well, I think we definitely meet your budget....;)
About Audio Analysis, we can't provide that but there are technology partners doing that with which we could integrate. It surely could be very interesting to integrate video and audio analysis, also right to attempt to reduce the alerts. For example, you could have a middleware correlating video and audio analytics (perhaps any "open" VMS can already do that..) and define a rule such as "aggression alert + shouting within 10 seconds = ALERT".
Merry Xmas to you all guys, have a great time