One or more mobile solutions is the sexy modern way to go, but it's not an either/or thing. If there's a good central location for an always-on monitor it's an excellent addition to the system. I had a great spot in my last house that everybody loved. It was easily viewed from the front entrance, kitchen, master bedroom door, and bathroom, and was in the center and got passed by everybody coming upstairs or to the living room. Heard a bang outside? Almost instant knowledge of what it was. Plus, you almost always knew when something was quietly going on in the yard, what the kids were doing outside, what animals were visiting, who just pulled up in a car to visit, etc. I don't have as good a location in my new house so I don't have an always-on central monitor and I really miss it. Wifey wants a TV in the kitchen in addition to the RAM iPad mount (iPads are the new cookbook dontcha know) so I might make that an always-on solution. She can just flip inputs if she wants to watch TV instead and flip back when she's done instead of turning it off.
