The Cusack Music Tap-A-Whirl is the world's first analog tremolo pedal with Tap Tempo built in. Now ALL units ship with Option Switch, and 24 waveforms!
Here are the major features of the pedal (see the manual for more details):

Tap your foot twice on the tempo switch to set the tempo.
Choose from 24 predefined wave forms, including:
sine, ramp, blip, bleep, square, waver, echo, and ping pong
Adjust the depth of the tremolo.
Brake: You can speed up or slow down the tempo by holding the tempo switch down.
The third knob can be configured to do one of two functions:
Fade in the tremolo effect, or
Change the speed at which the tempo is adjusted using the brake function.
This is set by moving a jumper, which is included with the pedal. The default setting is to change the tempo adjust speed.