[Amazfit] Poborak:
After quite some time of using Amazfit 2 as sportstracker mostly for running, I would like to share my experiences and comment on issues I have found. I have bought Amazfit 2 as a cheap replacement for garmin forerunner 220 I have used in the past. My feelings are quite mixed in the end. One of the highlights of amazfit is its build. It is build to last, looks nicely and fells durable in comparison with low to mid class garmin devices. However, there is lot of issues that in my opinion render it unusable for serious sport tracking:

GPS recording - There is discrepancy between mileage showed on watches (and in Amazfit app) vs mileage actually written in GPX file. So when your activity gets uploaded into Strava (or you then export it to Endomondo etc.), there is major difference (up to 2 %) in total mileage and thus also in pace etc. This is critical flaw.

Pace - One of the most important features of running sport tester is its ability to indicate current tempo. However, Amazfit readings fluctuate wildly, so it is really of not much use. For example, when jogging at constant pace, it quickly jumps between 4:00-5:30 min per km. In garmin devices, this get averaged and probably even anticipates hand movement, so you get quite good impression of how fast are you running at the moment. This is another major drawback of amazfit.

Altitude - I have noticed that for running, amazfit uses altitude from GPS only. Therefore, it is very inaccurate and completely useless - serves more like a random number generator. If you use "trail run" acitivity, altitude is measured through barometric sensor only, which is also less accurate. On garmin devices with barometer, altitude is measeured through combination of both sensors and measurements are very accurate (I got this impression after using Strava's correct elevation functionality).

Heart rate - For me, heart rate measurement during activity provides very poor readings. Even though i am having watches tightened fairly strong. For my regular runs at 150-160 bpm (measured through chest strap), typical stratos reading is around 120. Only sporadically, it gets closer to real values for certain period of workout. But in general, it is useless. It works same for my friend who also bought Amazfit for running. It seems to perform better when cycling (maybe because there is not that much hand movement - I dunno). However at this price tag, it is not realistic to expect any kind of accuracy from optical sensor. It is probably something very basic, it can be compared with garmin devices, which provide kind of realistic measurements. Downside of stratos is also the fact that it does not support ANT+ protocol, so most quality chest straps are not supported.

First beat features - These are in theory very nice. However as they are mostly based on HR readings, which are totaly offshot in Amazfit, they are not of much use.

However, this is something you might expect, as amazfit costs fraction of most other comparable devices, that can actually be used as sports tracker. In general, I would say, for a price it is still good buy for a nice looking smartwatch. For usage as sport tester, it has very nice hardware, however lacks proper software, which is probably not going to get changed.