Actually I think it's a very good idea. I know there are a number of aftermarket smart controls for electric water heaters, but I'm not aware of any that allow you to control the temp - but then I have not investigated them yet.
I'm in the middle of adapting my home to smart tech, I have modules to control lights and outlets, energy monitor, thermostat and security items installed at the moment along with an Amazon Echo. I think that by linking many of the things we do together there can be appreciative energy savings. Couple issues I see especially with adjusting the water heater temp for things like laundry is that it takes time to raise the temp of the water. If you do your laundry every Monday at 11 AM, fine you can tell your system to adjust for that. But for me it's a matter of when I feel like doing laundry, I have no set pattern. But that's me.For other things like morning showers and such that system can work quite well, especially if there is no one home during the day.
I'm sure that there are those that will rale against the tech, but I see so many possibilities. Cost is a major factor now, I did mine on the cheap - everything I bought was on clearance at very low prices or on sale at steep discount. But I have to say talking to my house makes some things easier.