This is, in theory, a good idea. You can stick your phone to glass and mirrors. This means in bedrooms and bathrooms, for example, it can be seen and better to play the radio, music etc.
I've used it a few times but was very careful on what would be underneath if it fell. It has now fallen off twice. Each time there was a soft surface below, a placed towel, but if there had been a hard surface it would have cracked my phone.
So, not used it again. I do use it to stick it to a table but it's too expensive for only that.
Overall, would you risk your iPhone for the relatively little benefit it brings?