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. 

 Are you thinking app or web? 
app is always tied up to the two major app stores... 

 Web.