Can't help but think this could be done without some Ethereum smart contract. Then again I also get the feeling this project would not get any attention without it. Isn't BT WiFi something in the UK like this? When someone has a BT router in their home you seem to be able to connect to it via the phone app.
You can see this in Singapore as well. The government there tried to use Ethereum to verify government documents: https://www.verify.gov.sg/
It's a bad idea. Slow. Much more costly. No benefit. Hard to scale. Downsides to tech flexibility.