Hot water controllers
 

I am in the process of choosing a hot water system and there a temperature controllers you can get for the instantaeous type of gas water heaters and I would like to know if they are of any real benefit. In theory they sound great being able to control the water temp in showers and not having to add cold water.
I am planning to combine them with the recirculators that only let hot water come out when you turn the tap on saving water.
Are they any good.?

Only real benefit of temperature controllers is the kids dont get burnt if they turn the shower or taps on by them selves !