When I bought my Fenix 6x 5 months ago, I never really planned to buy any accessories for it, but I've ended up adding a few over the months and learned that it often drastically changes my experience for the better when I do. What accessories have you added, or are thinking about adding, and why?
I first added a Tempe sensor. For $28, this is something I should have done at day one. It lets you measure accurate temperatures from anywhere you put the sensor, and assuming you put the sensor somewhere that isn't affected by body heat or direct sunlight, the temperature is completely accurate, unlike the internal sensor. If everyone should buy only one accessory, this should be it, in my opinion. Sometimes I'll even put the sensor on my patio so I can see the actual outdoor temp from my watch while I watch TV. Mostly it lives on the bottom of my backpack when I'm hiking or skiing.
Then I added an RD Pod. The sensor works great, but I've learned that I sorta don't care about the information it gives me. For the money it cost, I don't feel like I'm getting a great return. My vertical ratio, and ground contact balance, and all that, is neat info I suppose, but I really have no idea what to do with it. Unless you're a pro runner, this one is probably something most people can do without.
Chest Strap was next - I picked the HRM Dual, which is only a HRM, with no fluff. In hindsight, the HRM-Run would have been a better choice, since it incorporates most of the aformentioned RD Pod features, allowing you to only strap on one device instead of two, and the cost is about the same either way. Regardless of the strap you pick, it's a very valuable addition, and there are gazillions of threads about that. The OHR is hit or miss, it works well for me but not so great for others, and this takes it out of the equation completely and will always give you an accurate HR reading regardless of how well the OHR is or isn't working. At the very least, you'll have much smoother HR charts recorded with your activities.
Finally, I added an InReach Mini. As an avid backpacker, I can't believe I didn't add this sooner - and the Fenix integration is excellent. I can literally be standing on the south pole of the earth, and send and receive texts with a girl I met on ... from my wrist watch. Let me say that again - from my freaking wrist watch, I can talk to a girl from , while standing on the south pole of the earth 
As soon as you pair an InReach with your Fenix, you get a new datascreen on your activities, from which you can control your communications with your InReach. And the monthly plans are dirt cheap compared to a typical phone bill. It's an expensive device, but now that I have it, I wonder why I didn't get it from day one.
