The theory is, you run a loop out of the water heater, out to the fixtures, "T" right past the fixtures and bring it back to a "T" in the cold line inlet at the water heater. The water will be considerably cooler after traveling the entire circuit and the water pressure will still be on the street side so hot water backflow shouldn't be a problem. Keep in mind this will use more energy because the water heater will be circulating cooler water in at all times instead of just when the hot water is being used. Also, (keep in mind, I'm no plumber lol) I think if you add a check valve in a line where there is a heating device, you will have to add an expansion tank in the loop.
glennjanie is my personal authority on plumbing
I'm sure he will correct me if I'm wrong or add if I have left anything out.