Bests & Worsts Reviews from Amazon

I've owned three heart rate monitors (Polar, Zephyr and Mio) over the last 12 years and this product is by far the least reliable. Granted, this is the first HRM that took a reading from my wrist rather than my chest, it goes to show that the technology just isn't quite there yet. Very disappointing as I was looking forward to ditching the dreaded chest strap. Although it provided very reliable readings, it was uncomfortable to wear and often had to be readjusted frequently under vigorous activities such as trail running. The problem with the Mio is its reading often drops slowly from 150+ to 80-90 over the course of roughly a minute even if my activity level (and heart rate) remain virtually static. Sometimes it will shoot back up instantly to where it should be (150) or it will just sit at the 80-90 BPM level forever... or until I reset the HRM and reconnect again. On the chart, it looks like I literally stopped in my tracks and I just sat there resting while my heart rate slowly dropped... very misleading. While resetting it usually prevents the HRM from replicating the same problem during the same training session, it has dropped off several times in one training session before. I've tried to tighten the strap (to the point where it became uncomfortable) but that didn't help. There is also no correlation to ambient temperature, relative humidity or activity type (e.g. cycling, vigorous trail/mountain running or just jogging) as it will do it under all weather conditions and activity types I've subjected the HRM to. I think it may have something to do with a flaw in the algorithm used and less to do with it not being able to track the blood flow itself. Whatever the problem is, it makes a potentially decent product a major failure. The HRM would replicate this problem about 30% of the time I've used it (i.e. I would be forced to reset the HRM at least once in 1 out of 3 workouts) so I've completely given up in tracking/charting my workouts. It wouldn't be so bad if the device would disconnect itself completely (providing a "0" or "null" reading), subsequently leaving a gap in the workout. Instead, it will depict an 80-90 BPM range when I'm really pushing much harder. This completely screws up my training log. Outside of this major engineering design flaw, the watch itself also has other less critical but notable flaws which have been discussed by other reviewers on Amazon. The multi-color LED indicator light is too dim to see in bright sunlight - it is much easier to see the up or down arrows than the LED light so I'm assuming the light was added for people that train at night... but that could have been easily overcome with the simple addition of a backlight (which the product sorely needs). The loud beeping that accompanies the "zone training" can also be very annoying and there is no way to turn it off. The watch will tell you how many minutes you were "in the zone" but it doesn't tell you how many minutes you were "out of the zone" on the low end and out of the zone on the high end. That information would have been helpful in determining if I was pushing too hard or not pushing hard enough. Without it, you really don't have a clear picture of how you performed. Two of the three tiny nubs that stick out of the piece of plastic that lock the wrist strap in place have completely broken off. Luckily, the piece of plastic is small and is easy to replace. It would have been nice if Mio shipped the watch with a couple extras as they seem quite easy to break. I'll be hitting up Mio for replacement pieces soon as the watch is still under warranty. I would have given them 1 star as the erroneous readings make the product almost unusable to me but I give Mio credit for at least attempting to introduce a viable product the health and fitness industry sorely needs. I also understand not everyone is having the same issues I am having. The Mio does have an incredible battery life, is aesthetically pleasing to the eye and admittedly is very, very comfortable to wear. I'm hoping that their next version solves the reliability issues and maybe adds a few more features that are actually useful.