It all depends on what budget you are in, I have used many different units at different price levels and it all comes down to cost.
AVTECH (or CpCam) would be the most cost economic option, but I don't remember if is has the masking features that you are asking about.
Last year, I was beta testing a unit from GE security, the new Digia 2 series, and it has functions such as masking and something called network bandwith saving mode, which I believe is plays with the quality settings throught the video transmision over the network so that it achieves the best posible frame rate. This is a little on the high side, compared to AVTECH, but is something to keep in mind if the user is going to be using a AIRCARD to view the video. NO CDRW option on this one, but it does have a USB connection where you can backup the data and then use a PC to transfer the images to a CD.
http://www.gesecurity.com/portal/site/GESecurity/menuitem.f76d98ccce4cabed5efa421766030730?selectedID=11746&seriesyn=true&seriesID=
Another option, although I personally have not used them would be ICrealtime. Another member here can probably explain their features better than me. :wink: