I recently bought a iDVR-E4. Everything works great. I have it setup to access from the internet and also from my droid.
I have a dakota alert driveway sensor installed that has a normally open relay. According to the manual: "The relay will make closure for several seconds when an alert signal is received from the MURS Alert transmitter. The relay has a capacity of 5A @ 28V DC". The buried sensor is about 600' downhill from the house, but within sight.
I currently have several "chimes" attached, which are also from Dakota Alert. They have batteries, and chime when the relay activates.
I would like to connect the relay output to one of the alarm inputs on the iDVR, but there is not a lot of info in the manual as to what are acceptable voltages, etc. My understanding is that when the relay activates, that would store an alarm message on the iDVR, and I could see (with a PTZ camera pointed down the driveway) who comes and goes.