Here's my review of the mi band 3, It might be a bit long but probably worth it.
Using the band for more than 5 months
Let me begin by saying I wear the band all the time except bath. The band is supposed to be water resistant but I don't wanna dip it in a bucket of water. Have used it in rain, no issues.
-Beginning with the looks, the look of the mi band 3 is much better than it's previous generation. Looks sleek and nice and the edges are curved.
-Device - It's small and compact and light weight. The device fits the strap properly, also the strap doesn't get loose or gets removed automatically.
-Display and ui, It's a 0.78 inch OLED panel and with touch support. The ui is pretty well managed, you get used to it in couple of mins and not that difficult to navigate. YES it is visible in Sunlight.
-Customizations - Small things like screen lock and different clock faces give way for a bit of customization but not much. It can show notification icons like when not connected to bluetooth, when screen lock is enabled in band and when the battery is low.
-Steps tracking, Let me say that this is not 100% accurate and neither is any fitness band out there. But over all it does a pretty decent job at tracking the steps (At the end of the day just have a rough estimate of + - 100 steps from what you've got)
-In the recent update you will get a separate option for treadmill and exercise. Do note that these options tend to drain battery a bit faster because it uses the heart rate sensor continously.
-There are exercise options available, use that for workout. You can also use the mi fit app to start new exercise like cycling.
-Heart rate sensor - It works, not 10 times out of 10 but it works properly once it's properly placed in the wrist. (There was a major issue in the mi band 2 where the heart rate sensor won't work for people with dark colored skin but that's not the case here, it works properly)
--Sleep tracking, Surprising results for me. Sleep tracking does NOT work if you are taking a nap in the noon, only during the night. It was so accurate. Sometimes due to sleep movements it says you were awake during a particular period but that's OK (like hand movement or turning around in bed, and not always most of the time it knows but sometimes it thinks you're awake and in a couple of mins it says you're sleep again) .
-Connectivity - It connects via bluetooth and stays connected and the distance from the phone to band for connection is pretty decent. In android set this app for unoptimized battery use and I personally tend to keep the persistent notification (mi, oneplus users mainly) cause the os tend to close the app automatically and this was really irritating. If it's not connected you won't get any notification or anything.
-You can attend calls via the band, you can enable notification for all apps or even specific required apps. You CANNOT reply to messages and notification via the band. The band vibrates for notification and nonstop vibration for calls. But that's OK for me cause most of the time my phone will be in silent and only using the band I get to know I'm getting a call and vibration stops once the call is accepted or declined.
-Battery life - In the very first charge cycle, the band lasted me for around 13 days but after that it consistently lasts me over 15-20 days.
-I charge it usually in weekends twice a month. I don't honestly care about charging time. I just plug it into a computer usb port and check back after couple of hours.
-My usage might be different from others. I personally have manually turned of the automatic heart rate detection. I'd rather manually check my heart rate when needed. Also I have notifications only for messages and calls. Also I believe I have enabled night mode from 7pm to 7am (custom timing), it lowers the brightness of the display a bit during this time.
-Other than these there are options like stop watch, find device etc.
-One con, not really a con but yea here it is, finally after this usage my strap broke, have order a new one and waiting for it.
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