Create Hot Showerhead attachment.? Hello, While in a...

Hello,
While in a foreign country I see a device that allows you to turn the water that come out of the showerhead instantly into radiator water. I am traveling and would approaching to know if anyone knows where on earth I can find a similar device.

Again to reiterate. This is a device that one could either attach or install to the shower person in charge. The water that as a rule comes out will be cold.

Please find this device for me , I cannot find it any where.
I am building a unknown home and would...
Answers:    they hold them here in the US, they're call tankless water heaters.
they hold them at lowes and home depot.