The present inventions, in one aspect, are directed to a portable activity monitoring device adapted to couple to a body of a user, comprising a housing having a physical size/shape that is adapted to couple to the user's body, an altitude sensor to detect a change in altitude of the user and to generate data which is representative of the change in altitude of the user, and processing circuitry to calculate: (i) a number or flights of stairs traversed by the user using the data which is representative of a change in altitude of the user, and (ii) a state of an avatar using the data which is representative of the number or flights of stairs traversed by the user. The device also includes a display to output data which is representative of the state of the avatar.