If you go to the Noritz website you can pull down a pdf installation manual for one of their WH, the 69M for example. They have a diagram of an approved recirc system. I put in the tankless at the far end of the house as part of a remodel. Didnt choose to recirculate, but I have considered a Chilipepper recirc. pump or similar. Could use an X-10 outlet to control from some other point in the house. For the time being I just run the water as long as necessary; only the kitchen and laundry room are affected so this is not too critical.
If the hot water demand is large you might consider two mid-sized units like the 69M. These can be mounted in parallel and will self-control via a cable interface. I've been very happy with the unit so far (1 year). Love the constant temperature water.
Rick