I was about to build a prototype for this.
In my mind the basic is: download an open app store (eg: nostr:nprofile1qy2hwumn8ghj7erfw36x7tnsw43z7un9d3shjqpq0r8xl2njyepcw2zwv3a6dyufj4e4ajx86hz6v4ehu4gnpupxxp7slzk40u ), install Amber, create a new identity, install one mobile client (chat/social or both), login with Amber.
I'm focusing on the creating the profile, I think this is the first crucial step, then we can redirect the user to any app, web or native.
Amber is great, but unfortunately is not cross platform.