French based startup Enhancia were showing the prototype of their MIDI Ring Product, included here is the wired prototype, but the version which will be launched on Kickstarter in March 2018 will be a wireless version, using some kind of proprietary system.
The MIDI Ring allows for left right vibrato control, plus pitch bend - it can differentiate between the two gestures, plus a positional control which appears to be similar to Roland's D-Beam for an additional controller value.
At present it looks like the MIDI Ring will be priced somewhere in the region of 2-300$ at launch.
And viewer questions
Top end studio monitors?
New features, new patches
More hardware in the pipeline