Lieber Rob, not everything you haven't heard of yet, doesn't exist!
Wyman did play fretless too quite a bit, remember he was a double bass player at heart, but could never ever really play one because he found his hands too small. Hence his preference for short and medium scale basses and his penchant for playing his bass runs from the G string to the E string as opposed to the other way around like most electric bassists naturally do. He was always trying to emulate a double bass vibe. But he didn't do a lot of trademark slides - that is something only Jaco made de rigueur in modern fretless electric playing (a lot of Bad Company material was played with a fretless, yet you hardly ever hear a sliding note in Boz Burrell's playing on those recordings, there was a time when that was even regarded as a sloppy playing technique).
You've probably heard it more often on Stones songs than you think.
https://billwyman.com/2020/02/guitar-world-charts-history-of-fretless-bass-cites-bill-as-inventor/*******
As regards this breakthrough product itself, while there are certain aspects of rubber and plastic I like in an adult context, dental guards have mysteriously never been among them.
An unattractive contraption if I've ever seen one.
