How does the ones that connect to the pc work? Would I need to keep the pc on all the time? Can I make it wireless for this? I would like one with motion sensor (depending on the cost) I hear the wireless 2.4 Ghz frequency ones can be taped into. What about the standalone dvr or hard drive ones? For a non pc I would like to connect it to a portable tv and the camera mounted on the window sill. I wish to use one to protect my car when I am on holiday. What's the minimum I should spend?