The Fenix 6 is such an all measuring device, the only thing missing now is continuous glucose monitoring. I think it would be useful to know what your blood sugar levels are doing during exercise and help guide nutrition. The cheapest would be the Abbott sensor, $80-90 for 2 weeks, down side is it doesn't broadcast to your phone or , one day, the watch. Would have to wave the watch over it to dpwnload the glucose readings, much like the swim HR monitor. Other companies have much more expensive devices that broadcast continuously to your phone. I think it has to happen soon.