Yup; the Ubiquiti AirCam isn't sold as providing the features of motion detection.
Personally I purchased said IP cameras for weather watching.
The price of miniaturization of the required CPU power and OS and current algorhythms to process motion detection is still rather high and what you can get is just OK; but the race is on to provide better features at a lower cost.
Still even at $1000 a camera; the meat is not done relating to the science of motion detection.
Outdoors, relating to environment and using IR; its even more difficult.
Geez; especially when its snowing or raining or windy or when there are thousands of insects flying around (on a hot summer night for example).
The above written and noted it does sort of mangle the ability to use these features.
It can be almost done though; for a price.
That said its not a "perfect" science; it's very good these days; but its not soup yet.
Really though all I wanted to do was post an Aircam night picture of a video post processed en vivo using VLC as an example of what you can see with the Aircam at night.
My upload though is 1.8 Mb so its a bit too big. Here is a link instead.
https://www.dropbox.com/s/8u8vtuv8zxx1tys/vlcsnap-2013-02-24-23h39m47s184.png