The GUI seems very cool, I like the old analog look especially and it does seem well constructed. The thing for me personally is about what role would it play. First off it's not a regulation clock and definitely not going to be allowed for Tournament play. I and any tournament player already has to buy a regulation chess clock so this is not a cost saving alternative. This clock would actually be an added cost. With tournament use out we are left with this clock being used only for casual play. Most of of my casual play is done outdoors and I don't need to tell anyone about phone use outdoors in direct sunlight. So now for me its role is down to indoor use but not when I'm hike because as a tournament player I have a clock at home. You can see how niche it's usage is becoming. However to your point with using airplane mode you are correct that is a solution. I personally don't do that during casual play but that it is a solution. As to "don't talk and play" again this clock can't be used for tournaments so why not quickly pick up if the Mrs is calling?
@KineticPawn Very good points you raise. It's definitely a small niche market. Many (if not most) casual chess players don't use clocks. And if they want to experiment with chess clocks, there is a simple free one to download for their phone. Instead of chess clocks, casual players talk trash like: Move already! Geezus. OMG. There's nothing to think about, you only have one move. Goooo!!! Too weak. Too slow! You know, it's your turn, right? Haha! It's part of the fun. 
Here in NYC, you DO NOT want to put your $1000 iPhone in a cradle on a park table. I hope you have your running shoes on to chase after it. LOL
With all that said, there are people who will buy the Tempest clock for whatever reason. No need for anyone to try and convince people into buying it (or not). You either want it or you don't. Similar to my Red&Black mousepad board. It's a very small niche group of people who want a retro, cheezy looking Red&Black. But I'm glad there was an option out there for me to create and purchase the Red&Black mousepad board.
A few things I don't like about this. 1) Glare during outside games is going to be an issue. 2) What if you get a call? You would have to put your phone on airplane mode every time you used it.
I think you just put it in airplane mode. I mean what do you do when you get a call during a game right now? I hope you don't take the call 🤣 ... turn the phone on airplane / do not disturb whether this or any other clock. dont talk and play.
The GUI seems very cool, I like the old analog look especially and it does seem well constructed. The thing for me personally is about what role would it play. First off it's not a regulation clock and definitely not going to be allowed for Tournament play. I and any tournament player already has to buy a regulation chess clock so this is not a cost saving alternative. This clock would actually be an added cost. With tournament use out we are left with this clock being used only for casual play. Most of of my casual play is done outdoors and I don't need to tell anyone about phone use outdoors in direct sunlight. So now for me its role is down to indoor use but not when I'm hike because as a tournament player I have a clock at home. You can see how niche it's usage is becoming. However to your point with using airplane mode you are correct that is a solution. I personally don't do that during casual play but that it is a solution. As to "don't talk and play" again this clock can't be used for tournaments so why not quickly pick up if the Mrs is calling?