iOS Software Link to custom OS

*I would like to start by saying sorry if I posted this in the wrong sub, I'm new to this whole thing.

I want to connect my iPhone (using an app, that I am yet to develop) to a Raspberry Pi Zero W that is running a certain OS (That I haven't started on yet). The iPhone app should be able to connect to the Pi using Bluetooth and my plan is for notifications received on my phone to appear on my Pi display. I would also like to change settings on the Pi from the iOS app. My plan is to put the Pi into smart glasses if that's important.

How can I get started doing this? Is this something I would be able to achieve? Any help would be appreciated!