I used a fish tank pump with surgical tubing and a moisture sensor with an arduino to switch the pump on when it got dry but as you say, its never that easy, the whole thing is lying in a drawer somewhere, it didn't make anything easier. Another project involved load cells and LPG gas bottles. That was a bit more useful but it needed to be constantly powered and the wires kept falling out, so that's also in a drawer somewhere. I still haven't made a useful project yet
