I had motion detection set on the cctv system I had at work and that was controlled from the dvr, it only recorded when movement was detected to reduce the amount of data stored. When a spider built a web across a camera it would record all the time and I had to block out areas where shrubs/long grass would move in the wind.
On that system the cameras were on all the time and recording was triggered and I imagine that is how it would work on most of the cameras we use. Presumably it is a function that can be built into the camera to enable it to send pictures and alarms over the internet or mobile phone. I've never seen a reference to how it might work in any of the listings for ordinary cameras but Sure24 might well be able to provide more informed advice.