I took a closer look at that camera, seems it has a button for switching camera's, not split screen. I'll look around on that site a little more and see if I can't find one. If it's available, I think it would be alot easier if it were motion sensitive too so she wouldn't have to go through 24 hours of footage every day as well. Of course, she would only have to look over it if she suspected something, but then again they could be doing other things she may not find out about. I think it would save her money on DVD's too.
EDIT: Ugh, two other things I just noticed - DVD's even though they have 4.7GB of storage, list there video recording time of 120min. Anyone know if that time changes depending on the quality of the video? You don't have many options for customizing how to record with a DVD player, not like a computer anyway.
Other thing I was thinking about - even if there is a motion sensor attached, the DVD player will be recording 24/7, the motion sensor wouldn't turn the DVD recorder on/off, so it sort of defeats the purpose of saving space and effort of looking through the footage.