Google's own carrier, Project Fi, is a pretty great service if you don't use much data. However, the lack of affordable devices compatible with Fi (unless you can find a non-bootlooping Nexus 5X) has made it a bit less popular. If you're on Project Fi and using a group plan, you can now easily split up your phone bill.
If you're not familiar with Project Fi, the carrier began offering group plans in October, with up to six lines supported. Now you can manage repayment for group plan members, with three options available - the full cost incurred by the person, a fixed amount, or the cost of additional data used past the budget.
When it's time to pay the bill, Project Fi can send payment reminders to each person. Once they get the notification, they can just tap 'Send money' to repay the group plan owner (if they have a payment method added to Gooogle Wallet). This feature is rolling out starting today, and will be available to all Fi users by the end of the week.