On the one hand there is actually nothing to stop you just entering a street name and omitting your residence number - I think it will still setup the notice board and email group exactly the same.
And there is nothing to stop anyone from putting in some other street number than their own. There's no easy way to validate the correctness of that info - and it would be invasive to try.
There might be something useful that can be done with the street number though, I'm not sure. The flexibility of the geographic boundary is basically as general as the google maps API search. So it can be very broad.
As far as yoga groups or parents school groups etc are concerned, it seems like that domain is covered by FB...
I'm keen on fostering better street communities. Very light connections. Making it possible to do things like borrowing tools from each other, or creating a little veggie garden for the street, encouraging the sharing of resources with your neighbours. There's so much overlap and waste with everything...
And e.g. you probably wouldn't lend your spade to some random in your neighbourhood, but maybe lending it to the guy who lives across the road, is less of a big deal. After all - you know where he lives.
Love what you said about having a feel good story, and creating an example notice board page. Thank you will do!