The Collaborative International Dictionary of English v.0.48:

Pedometer \Pe*dom"e*ter\, n. [Pedi-, pedo- + -meter: cf. F.
   p['e]dom[`e]tre.] (Mech.)
   An instrument for including the number of steps in walking,
   and so ascertaining the distance passed over. It is usually
   in the form of a watch; an oscillating weight by the motion
   of the body causes the index to advance a certain distance at
   each step.
   [1913 Webster] Pedometric

WordNet (r) 3.0 (2006):

pedometer
    n 1: measuring instrument for recording the number of steps
         taken in walking