Auto-pay at Pump / Gas Monitor
I think it would be pretty convenient to have the same technology that is now in 'tap' credit cards, implemented into gas nozzles and tanks in your car.
The nozzle on the pump would have a sensor to gather billing info, that would be recieved from another chip mounted just inside your car where you place the pump.
When your finished some info should be collected by your car:
Price paid for gas, how many gallons, date etc.
Your car could then compare that info to your mileage, giving you a more accurate gas mileage reading, plus info like how much gas you use on average a week. How much you spend in gas per week..month..year..etc. Just real time data so you can know what your spending. Maybe even gather data to compare what you pay to a national avg just for fun.
(of course all data should be downloadable to whatever flash drive, or emailed to you)
Seems like the technology is already there. It would also save sitting at home with a calculator trying to figure out if i can afford the gas in my car, or if i need something more economic. It would just be a really nice feature.
Reward: The convenience would be a reward.