This sentence sure made me think of those iPods:

A single, manually operable rocker-pad (30) centrally mounted upon the pivot support (32) such that said Rocker-pad (30) is pivotable in respective right-angle directions responsive to manipulation by the thrumb. The combination of the small size of the casement and the position of the rocker-pad enables a user to grip the recording device with one hand and easily manipulate the rocker-pad with the thumb of the gripping hand to selectively execute any of a plurality of command schemes.