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Most of the apps i can think of that would be useful require connection to some sort of DB or service. I'm assuming you're going to host something for that? Like a DB and a webserver, or a some sort of cloud deployment
If so, how about something that automatically shows your closest friends/family? and allows you to set up radiusus for what constitutes "closest"?
you could do group chats and/or organize meets using it.
Building the app is the easy (or at least the relatively easier) part of the bigger picture. The challenge is in finding the first solution to a business problem that's costing companies millions (or billions). Since you have the experience and skills to build a software product, I recommend seeking a dev/architect position in an early stage company that has (or is close to having) stage 1 funding. The rewards (both professional and monetary) can be significant. I strongly recommend not trying to find solutions to business problems - you won't have time to do any development if you're busy doing that.