If you have the walls open and access to the pipes anyway (say you're doing a full kitchen reno), it can be a worthy project. Just like ChrisF said, the hot water line must be well-insulated. I actually think the return line SHOULDN'T be insulated, because as it's allowed to cool it will pull heated water through the loop by convection. This will provide hotter water faster at a cost of running your tank heater more.
If you don't have access to the pipes, there are still a couple of options. The Hot Water Lobster is a flow-control valve that goes between the hot and cold supply pipes of the furthest run from the tank. When the water on the hot side drops below a settable temperature threshold, the valve opens to allow the cooled water to return through the cold water leg (which after all is connected to the HWH as well). The downside of this system is that your cold water will be warmer, and it's not as efficient as a dedicated return loop.
You can also use an electric point-of-use heater, like this one. This will hook to the supply line under the sink (or wherever) and keep a small amount of water ready for instant use, which should be enough to last until the hot water from your main HWH gets to that faucet. The one I linked to only draws 1500W, which is just a little more than a 15A breaker should have on it (80% of breaking amperage = 1440W, but theoretically the breaker won't trip until 1800W). So, you'll want a dedicated 20A breaker for a heater like this.