I find sleep tracking to be really useful. One thing that surprised me has been seeing the affects of either alcohol or caffeine on the type and quality of the

I find sleep tracking to be really useful. One thing that surprised me has been seeing the affects of either alcohol or caffeine on the type and quality of the sleep I get. Even if the absolute numbers aren't 100% accurate the watch definitely spots when I've had even 1 beer during the evening. I also find heart rate variability interesting. I can't put much spin on the absolute numbers but after either heavy exercise or if I've been unwell I can see the variability rate really drop.