Set up a smart contract to share an unlimited WiFi connection with neighbours, flatmates, etc., with billing divided by amount of data usage.
John uses 200 GB in a month, Alice uses 100 GB, Peter uses 50 GB and Ashley uses 50 GB.
Split the bill in the ratio 200:100:50:50 = 4:2:1:1 between John, Alice, Peter, and Ashley, respectively. E.g. for a $100 monthly bill, John pays $50, Alice pays $25, and Peter and Ashley pay $12.50l
Have custom options for the owner to set the maximum number of users at any time (useful if it gets too slow with too many users).