They are called "circulators," and yes, they are an excellent idea that was actually used in conjunction with the existing bus system back in the 70s and '80s.  The train should run in a direct line from here to there, and people along the way should be able to use LOCAL circulators to get to the stops.  As an example, look at the Anschutz campus.  The train could not run through the middle of it, so it runs well north, but there are small, blue busses that circulate about the campus and take people to the stop.
(cont'd.)