I love this "local first" focus, which for me translates into "relevant first". My app Plantshare (posted about it in this HN post) is not very useful if you're the only user for 40km around, but I've seen local pockets of signups that gain momentum and are then useful in that locality and the users make local connections.

I think the biggest hurdle for this would be to gain traffic in place of an existing entrenched local Facebook group or similar.