> Also there is privacy angle, I don't think nobody wants pinging their location all the time, maybe some QR code/ beacon solutions can help, but I am not much optimistic there too.
Maybe you could have something like K-anonymity? You discretize your location into chunks of maybe 100x100 m, take the hash of the chunk ID, and request results for all chunks whose hash starts with the same 4 or 5 digits as your chunk's hash.
Would probably require some more thinking since a consecutive series of requests for adjacent chunks could be used to uncover which particular chunks you were interested in.
Maybe you could have something like K-anonymity? You discretize your location into chunks of maybe 100x100 m, take the hash of the chunk ID, and request results for all chunks whose hash starts with the same 4 or 5 digits as your chunk's hash.
Would probably require some more thinking since a consecutive series of requests for adjacent chunks could be used to uncover which particular chunks you were interested in.