The Sensewah is an envelope filter for producing an autowah effect and what T-Rex calls a 'yoy yoy' - it's similar but with more high frequency content. A sense knob determines how much effect you get while the range knob sets the width of swept frequencies.
Juxtaposition of the two knobs gives a useful range of automatic wah sounds that respond to player dynamics. While others could find a use for it, this is really tailor-made for funk players looking for consistently rhythmic wah sounds to fit a groove and a bit of 'quack' when digging into single notes.
If you'd rather concentrate on what your hands are doing (or your dance moves!) than manually control a treadle, this pedal will let you get funky.