[fintstone]

I use a RedyTemp ATC3000 Hot Water Circulator on-Demand Circulation Recirculation Pump in my vacation home (regular hot water heater, not tankless). I mostly use it because it keeps the pipes from freezing in the winter. I can remotely turn it on from anywhere (and the hot water heater...also on a wemo switch). I leave both off when I am away and it is not cold out (enough for pipes to freeze). Just place it at the faucet that is farthest away from the hot water heater in the circuit...and it will fix your problem for all in between. It is not cheap to buy, but is safe, well engineered, high quality, easy to install, and saves water and electricity. I use a wemo plug-in to control it from my iPhone, but it comes with a timer if you prefer. You can also use a motion sensor or a switch (if you prefer) to use whenever you go in the bathroom and by the time you get your clothes off...hot water. When I ordered it...it took a few weeks and i began to worry...but then it arrived. Guess the guy sells them out of his house or something.

They also sell a version for tankless water heaters.