Single pedal kickbox (one I have)
Double pedal kickbox
You can use any electronic drum kick trigger. Some recommended ones are the Roland KD8 and the Yamaha KP65.
I personally use a KD7 because I got it for cheap. KD7 isn't bad, but it requires a reverse drum beater to use. You can't use the standard drum beaters that come with drum pedals. If you care, I use the Pearl P-120P pedal.