Actually, that's a good question. I switch between Android and Apple all the time and sometimes forget the apps don't match up. It's an Android app that tells me that information. But I would imagine it's similar with the iPhone as far as my router changing output. That's also what the tech who installed it told me. I can verify it on my Android by walking away from the router and when I get far enough away it automatically switch's over. Sorry if I was misleading.
The app is called signal spy and now that Google fi accepts certain iPhones in their system I'm wondering why the app wouldn't be available on the app store because it goes hand-in-hand with Google fi. Very handy app indeed.