Download on Google Play
For a year or so I used the
NextBus application to track my transit, until they discontinued support for the MBTA. I couldn't find a good replacement that I liked that was both free and without ads, so I made my own.
Originally, it was just part of this website, and only supported a pre-set list of routes that I configured for myself, but to make it available to more people I published it and added general MBTA tracking support.