We have a mouse in the house. I wanted to have the little intruder on camera. I dug out the old webcam and started to google for webcam motion detection software. Unfortunately a free but closed source program (Yawcam) won over a open source one (Dorgem). You can see the results in the video above.
The mouse makes its appearances at 3:00am, 3:50am and 5:26am. I forgot to add in time stamps to the images, but Yawcam can do that.
Dorgem was not satisfactory because I couldn't get motion detection to work. There was no way to adjust the threshold. I set it to take shots every 1s and it saved images with time stamped filenames (and a time stamp on the image itself) but the motion detection did not work. Perhaps the CCD noise kept triggering the software, I just got image dumps regularly at the 1s rate. [Help page on how to use Dorgem for motion detection]
Yawcam is more professionally designed. It has a motion detection preview pane where you can adjust thresholds or have the software adjust it automatically. The software highlights in real-time parts of the image where it detects motion. I found the auto-set tolerance level (20%) to be a bit high, perhaps because my motion trigger - a mouse - occupied a small part of the frame. I set the tolerance to 5% and the threshold to 95%.
Yawcam logs each motion event with several useful parameters. It has a "motion %". The first mouse appearance is triggered by a value of 5%. In contrast me walking across the kitchen is at 48%. My guess is that the % is the percentage of the screen that goes above motion detection threshold.