I can think of numerous ways to make an excessively complex electronic shower control that don't involve a smartphone and cannot think of a single benefit of integration with a phone. I'm not some old fart who refuses to use newfangled tech either, I love my smartphone but this is such a completely moronic idea that I don't even know where to start.
It reminds me of those horrid climate controls in cars, I've never used one that worked worth a damn, they all seem to want to turn the fan on full blast and fail miserably by trying to control the ambient temperature in what is effectively an uninsulated greenhouse rather than controlling the temperature of the air coming out the vents. None of them work as well as a simple mixer valve and manual fan control. This shower is a similar gimmick, technology for the sake of technology, not because there's a problem that needs solving.