Electronic Alarms and Home Security Devices - Front Door Monitoring

Looking for a way to monitor who is at the front door without having to always go to the door and see. I've found a few "door bell" units with a cam and monitor, but not sure what the best choices are.....

Also thought of setting up a cam (wire/wireless) so that we could see on a tv or computer in the house. Guess it would be nice to have an intercom function to tell the salesmen to go away.

Please give me your thoughts on this issue, including any experiences (good/bad) you've had setting up something like this....


Thanks
Dan

I've seen a couple of setups where the input from a camera has been fed into the secondary video input. When someone comes to the door, they use the PIP function to "peek".