The Exit Index from Death By Audio is an all analog tremolo with blendable distortion.
Presumed untamable yet incredibly interactive and wicked cool, the Exit Index is great for expressing melancholy love and makes you turn your at-first pedal testing blues licks into droning arpeggios.
Four knobs - Romance, Fantasy, Honey, and Blood - respectively control your input signal, effect blend, tremolo speed and distortion level (simultaneously), and LFO intensity. And yes, those "helicopter" sounds are intentional! There is also a 2-way toggle to select slower or faster tremolo speeds.
The tremolo speed on the Exit Index is not consistent, and ramps up or down based on pick dynamics, and input signal. It also acts as its own gate to bring the modulated signal in or out, even if you bring in the pedal's distortion.
Sort of like the Russian Reversal, in this case, "Pedal plays you!" If you want a pedal that responds to your playing and in a way tells you what to do next, put this on your board.