BLE interface with iPhone

Yes, it'll definitely connect, and there are a few options that I know of:

• Write an iPhone app - but this could be a steep learning curve and you need a developer subscription
  
• Make it into a Bluetooth keyboard - that'll work fine to control an iPhone, but I'm not sure you can get any useful data back out of it
  
• There may be an existing app you could use...
  
  • I don't know if something like Blynk can be made to do what you want. If you're interested in this let me know as I've intended to figure it out and do a tutorial for a while.
    
  • The Adafruit Bluefruit app can talk to Espruino pretty easily, but I don't know if that'll integrate usefully with iOS notifications.
    
• Use the WebBLE app which implements Web Bluetooth - so you can write a webpage that'll then control the Pixl. I'd definitely recommend that as it's really flexible, but it's not something that can run in the background so wouldn't do notifications.
  
  

Hope that helps!