Realistically, they'll build FediHood against Mastodon and its inner workings and call it a day.
Friendica, Hubzilla, (streams) and Forte all have (partly optional) dedicated profile fields for your location (street, town, postal code, region/state, nation, Facebook-style "hometown" as in place of origin). FediHood could use these. But, like so often, I've got my doubts that the makers of FediHood even only know that Friendica exists.
I mean, if they really knew even only Friendica and Hubzilla, they would have made FediHood a third-party add-on for Hubzilla.