Eventide's hugely popular H9 Harmonizer has now landed itself a product-specific expression pedal courtesy of Mission Engineering.
The SP-H9 is specifically calibrated for the H9, and features an integrated switch to engage repeats and other H9 functions, plus an external aux switch input for remote tap tempo and flex control.
A single TRS cable connection hooks the SP up to the H9, and also provides power to the expression pedal's LED status indicator.
If you have an H9 and want to express yourself, the SP-H9 seems like a no-brainer - it's available now for $139.