The title should say an easier way to pay for public transit ...

I know that the buses running within the confines of downtown is free, but trips from downtown to/from other parts of the city are not free and currently the T only take exact change. I think a big step in encouraging the use of public transit and allow more people to connect via downtown and come to downtown is to implement some sort of google wallet/apple passbook type payment system where the passengers can paid via their smart phone or through some kind of prepaid card.