I created the twitter feed based on a JSON feed of the geographic location of the minibus provided by my colleague. I then compare the coordinates of the minibus with a set of bounding boxes stored in a database. If the bus is within squares defined in the database, then the pre-defined description is sent to twitter so that anyone following the bus can receive updates as to where it is.

The current set of boxes are the bus stops on route and the car park back on site.

One possible future enhancements could be to allow you to subscribe to a particular bus stop and receive a twitter direct message so that you know when the bus arrives at that particular bus stop.