1. A mobile-device-based system for classifying a mode of transportation during a trip, the system comprising: a mobile device including a location detection system and an accelerometer, wherein the mobile device is configured to collect location data and acceleration data during the trip; and a data processing block configured to: receive the location data from the mobile device; receive contextual data related to a plurality of transportation systems; process the location data and at least a portion of the contextual data using a first transportation mode classifier associated with a first of the plurality of transportation systems; process the location data and at least a second portion of the contextual data using a second transportation mode classifier associated with a second of the plurality of transportation systems; receive a first transportation mode metric from the first transportation mode classifier; receive a second transportation mode metric from the second transportation mode classifier; classify the mode of transportation during the trip based on the greater of the first transportation mode metric or the second transportation mode metric; display the classified mode of transportation to a user; receive a verification of the classified mode of transportation from the user; and update at least one of the first transportation mode classifier or the second transportation mode classifier based on the received verification.