I think open source software can provide enormous peace of mind when you're in control of downloading, verifying, and installing specific software. I'm not so sure this is nearly as applicable for mobile apps. I mean, supposedly the respective App Stores verify author signatures... but even so, I don't feel like I have much hope for knowing what it is that even gets installed with each update.

I don't think it's a reasonable ask to expect Bitkey users to keep tabs on the state of the software that's running on their phones (open source or not) - especially when the whole point of using a Bitkey is so they don't even have to worry about keeping track of a few seed words.