This is clearly a solution looking for a problem. It would have been great fun when I was about 7 years old though, to screw with the temperature from another room while my dad was taking a shower. I really cannot picture a genuine use case for such a technology, I certainly don't bring my phone into the shower with me, and I don't need to run the shower if I'm not physically in the bathroom to use it. If I wanted instant hot water I could install a point of use instant water heater or a recirculation system that pumps the water in a loop from the water heater to the shower valve. My friend has that in his house, it can be set on a timer or you push a button when you walk into the bathroom, then by the time you're undressed you just turn on the shower and the water is hot.