iSight room monitor


I have a 90 year old mother who tells me someone is calling her on the phone at night and/or ringing the doorbell or knocking at the door. She has an iMac with an iSight camera.

What I would like to do is use the computer to monitor the activity at night. I would like to have the camera activated by motion or sound above a certain db level and record until motion stops or until the sound stops.

This is driving me nuts, as they only seem to ring the phone once, so caller id doesn't work to trace who is doing this. I have spoken to the local police who say they are doing more frequent patrols past her home, all to no avail.

Can anyone help?