I agree, it seems rather risky to not have some type of monitoring going on. And your idea sounds pretty decent. Just some quick go/no go visual indication. Thats simpler and just as effective for the purposes making sure everything thing is in working order. I suppose even something to make sure that pump is working too would work. Of course if it does stop working obviously your temps are going up real quick, but it may afford you the extra few seconds or so to drop out of a run and shut things down.
If I was going to monitor the pump, it would have to be something that would monitor the rotation or pump action rather than a voltage/current flow. Id rather know the thing is spinning over whether or not there is current flowing.
