A tool, similar to google maps' "get directions by public transport", but which permits the user the choice between:
"Do I want to walk to/from the stop/station" or
"Do I want to bike to/from the stop/station", and possibly even to be able to specify that "I am willing to walk/bike a distance of x miles to get to/from the stop/station".
By biking I can choose from a vastly larger range of potential stops/stations, and can thus attain, from my point of view, a much more efficient usage of the offered public transport.
It would still be important for me to be able to choose "I want to use trains only" (because I have an odd-sized bike that doesn't fit in buses' bike racks).