I've built a tool to help foiling (and soon sailing windsurfing ecc) athletes analyze the data from their Garmin
I've been building Varea, it's a free web app that takes your Garmin .FIT files and turns them into useful tactical analysis for sailing and foiling. Wind direction calculated via an API call to a meteo service, tack/gybe detection with entry/exit speed, VMG breakdown, foiling ratio, start analysis, polar chart. No hardware needed, just upload the file your watch already records.
It's aimed at athletes or coaches that are willing to use data that they already have on hand, but that's it's hard to understand and use, to improve.
It's still an MVP so it's gonna bit slow in the part where it analyzes the data but I'll work on it if i get some traction, also I've just finished setting it up in english so I'd be grateful if you tell me if you find any mistakes or if you know of some features that would be useful!!