https://genkiinstruments.com/wave/
It is a ring that sends midi control signals which may be useful for control a filter, formants, effects, cross modulation, etc.
This would work better for my style of play since the index finger is away from the antenna the issue being which axis of motion is controlling what parameter.
A foot switch to turn the ring on and off would be preferable.
Sounds like a fun nightmare, for someone who uses synths with the theremin.
