Gesture Synth (gesture-synth.net)

Gesture Synth at gesture-synth.net describes a gesture synth as an electronic instrument controlled through movement, and recognises stable one-to-five finger shapes.

The emphasis on stable shapes is worth noting. Finger-count detection that fires on every frame produces unwanted notes as your hand moves between positions, so a stability requirement is a design choice about playability rather than a marketing line.

Details below are taken from the site's own published description rather than hands-on testing.