Maybe not the most straight forward answer but you should be able to get it running based on those two posts.
First is Web Bluetooth app connecting to a gyro device and visualising using three.js. Its not an espruino device but you should get the idea.
Second is Web Bluetooth app connecting to espruino Bangle watch and visualising using tinydash.
So using bits from both examples you should be able to do what you want. I want to make a version for the second demo using three.js but its not going to be any time soon.
Hope that helps.