You may want to consider the iOS-friendly Logitech Alert system. Logitech offers a range of "smart" security cameras that can detect motion, stream video and send alerts. Its free iOS client works with these security cameras to let you remotely watch live video streams, enable or disable the cameras' motion alerts and check your camera status while on-the-go.
NightOwl produces another line of security cameras. For about US$350, you can pick up a package of four indoor/outdoor night-vision capable CCDs that appear to work with any mobile browser, including any iPhone or 3G iPad.
It sounds to Auntie, however, as if you've already got a computer set up and running the DVR. If so, a simple remote access client, like LogMeIn or iTeleport, can help to control that computer from iOS.
This solution might not provide as smooth an experience as the Logitech turnkey approach, but it could get you past any monitoring-while-on-the-go issues, assuming that you have enough bandwidth to work with. Both apps are bandwidth hungry, especially when your screens update regularly with video.
As a final note, if you're running your DVR on a Macintosh, you might want to look into SecuritySpy. It's a multi-camera surveillance app that coordinates with Mac OS X-friendly CCTV cameras.