Nitinol Drain Closer Idea

[Ryland]

I had a thought today as I was filling the bath room sink with warm water.

Wouldn't it be nice if the drain stopper closed on it's own, a spring would default it to closed, but a Nitinol spring in the drain pipe would pop it closed once warm water hit it, so the drain stopper would close and the sink would start filling wasting as little warm water as possible.

I think a foot of Nitinol wire would be enough for a spring and it costs 50 cents per foot, so all and all it would be cheap to have as an option.