Mio SLICE Heart Rate Fitness Tracker – User Review | GadFit Singapore

February 11, 2017

Originally slated for release a year back, the Mio SLICE ($129.95) finally arrived this month. Featuring all day activity tracking, Mio’s proprietary PAI score backed by the HUNT study, and broadcasting of heart rate data via ANT+ and Bluetooth Low Energy to select devices, this was to be Mio’s pièce de résistance.

I finally took receipt of this long awaited device about a week back and here’s what I have to say.



  • Unique PAI score based on HUNT study
  • Wrist based heart rate measurement
  • All day activity tracker. Records steps, distance, calories burned, sleep, all day HR and PAI score
  • 5 days battery life span
  • Vibration enabled for smart notifications
  • Stores heart rate data at 1 second intervals during exercise, every 5 minutes below moderate activity, and every 15 minutes during sleep.
  • Bluetooth Low Energy and ANT+ enabled
  • Transmits HR data to compatible devices and mobile apps
  • Water resistant to 3 ATM


  • Display not visible under bright daylight
  • Unable to set alarms or sedentary alerts
  • Workouts not exportable from native app for now
  • Generic workout only, can’t add type of workout
  • Advertised as 5 days battery life but only lasts about 2.5 days
  • Non changeable wristbands
  • Limited compatibility with 3rd party apps for now


The Mio SLICE features a wearable core that’s built with the wrist straps. What this basically means is that the straps are non-changeable.Mio SLICE front and top viewThe wearable displays the company’s proprietary PAI scores for the user with options to further show steps, calories, distance and sleep. Users can also access real time heart rate at rest and during workouts.

Connectivity to compatible mobile devices is via Bluetooth though the Mio SLICE is also capable of broadcasting HR data via both ANT+ and Bluetooth Low Energy; a familiar and key feature of Mio devices.wrist clasp of Mio SLICEA single button controls the wearable with short and long presses. The OLED screen performs decently under low light conditions and room lighting.Mio SLICE multiple viewsBut out in the bright daylight, it fails miserably; I actually thought the device ran out of batteries because the screen was blank. Users can adjust screen brightness levels but setting it to “high” did little in terms of visibility under bright day light.The back of the Mio SLICE houses the optical heart rate sensors and the charging port. I went from 0% to full charge in under an hour.According to Mio Global, a full charge runs the device up to 5 days though I only managed 2.5 days at best with 30 minutes of workout daily and SMS text alerts turned off.

Mio SLICE is also rated at 3ATM water resistance.


The Mio SLICE is an all day activity tracker that is capable of tracking steps, distance, calories, sleep and Mio’s proprietary PAI score, backed by the HUNT study.

PAI Score

The company first announced this metric about a year back and released a PAI mobile app capable of computing PAI scores from Mio hardware. I tried the mobile app back then and assessed it to be a novel effort to inject an alternate and credible perspective to the ubiquitous step count.

Daily activities contribute to the accumulation of PAI scores with activities that put the heart to work garnering more points than activities like strolling where the heart rate is mildly elevated, if at all.

To illustrate this, my 30 minutes spin bike session which had my average heart rate at 155 with a maximum of 177 net me 24 PAI points while an entire day of moving around to the tune of 10,000 steps only net me 5 PAI points.

This might prove discouraging to those who’ve made it their life long goal to score 15,000 steps per day only to be shown that it doesn’t count for much. There’s no cause for worry as the Mio SLICE tracks steps as well.

Heart Rate Accuracy

In order to compare the HR accuracy, I had to connect and transmit the heart rate data from a Mio SLICE to a Garmin Vivoactive HR via ANT+ and compare it versus a Polar H7 running with Polar Beat. Mio SLICE can also transmit heart rate via BLE to compatible mobile apps. There are 2 tests I usually do, a flat surface run and a interval session usually involving the elliptical machine or spin bike.Mio SLICE vs Polar H7On both occasions, I found the heart rate readings from the Mio SLICE comparable to that of the Polar H7; a tad delayed but within a few beats.

Workout Mode

In workout mode, users can see elapsed time, current HR and PAI score for the session. The wearable will also sync the workout session to the Mio PAI 2 mobile app.

Users can choose to have the HR data transmitted via ANT+. This feature can be enabled under “Settings.” The Mio SLICE must be in workout mode for ANT+ broadcasting to work.

I was able to pair the device easily with my Garmin Vivoactive HR during my test workouts.Mio SLICE workout mode timerTransmission of HR data can also be done via BLE to select mobile apps such as Strava (premium version only) and Endomondo. This can be done by toggling the Mio SLICE to HR mode or workout mode.

PAI 2 Mobile app

Mio Global now has the Mio GO, Mio PAI and Mio PAI 2 app, each serving different purposes. I’m sure consumers will inevitably be thrown off by the numerous mobile apps Mio dished out.

The Mio SLICE connects to the Mio PAI 2 mobile app only.

Users can customise stats such as steps, calories and distance, to be displayed on the Mio SLICE device from the Mio PAI 2 mobile app. Settings for display brightness levels and extent of smart notifications can also be customised here.

The mobile app is unimpressive and mediocre at best with only daily views available, not weeks nor months. Users can manually add workouts on the Mio PAI 2 mobile app but not dictate the type of activity, only the intensity. This again serves to emphasize how particular Mio is about their PAI ecosystem; the importance of how hard you work rather than what you do.

All Day Activity tracking

Besides PAI score, the Mio SLICE also tracks steps, calories, distance and sleep. The wearable will also track resting heart rate during sleep and update the readings in the mobile app.

From my experience, sleep tracking was captured on the Mio SLICE device but not properly synced to the mobile app. As of publication, only 1 night’s worth of sleep out of 6 was recorded in app. But I understand this has been fixed with a firmware update. I’ll update this after another week of use.

Smart notifications

The Mio SLICE is capable of displaying truncated SMS text messages and calender notifications. Caller IDs will also appear when phone calls from contacts pops up.

At present, truncated notifications cannot be expanded so users will still have to rely on their mobile devices.

Vibration alerts

The company does have plans for utilising the vibrations for setting alarms in the future though no concrete dates were provided.


Mio took the best features of their optical HR sensor technology and packaged it in a svelte all day activity tracker compared to its predecessors. Users of the Mio Alpha 2 or the Mio Fuse would remember how big those devices were! The company also went the whole nine yards by backing their proprietary PAI scores with the reputable HUNT study and retained the HR transmitting features.

You have to give Mio due credit for that.Yet while I applaud Mio Global for championing their proprietary PAI scores , I can’t help but be reminded of NikeFuel which made little sense to people outside the ecosystem. This move may further distance Mio from consumers since the emphasis is on something novel (Mio PAI) rather than familiar (heart rate and steps).

A few bugbear to note. I was appalled at the performance of the display screen under normal daylight in the outdoors and actually thought the device had run of out juice.The battery life is listed as 5 days but I only managed about 2.5 days despite only using it for normal wear with 30 minutes of workout per day and subdued smart notifications. (Only enabling phone calls)

These are a few more issues I faced when using the Mio SLICE this week.

  • The Mio SLICE buzzed upon reaching 100 PAI, even in the wee hours of the morning (supposedly fixed after firmware update, didn’t manage to test)
  • Sleep tracking does not sync properly to the mobile app (supposedly fixed after firmware update, didn’t work for me)
  • Mio SLICE tracked that I was asleep for 13 hours straight even though I was at work as a Physical Education teacher teaching sports!

Mio has indicated they have a series of updates in store to optimise the Mio SLICE. True enough, midway through my review, my Mio SLICE received a firmware update which made activity tracking more tolerable.

Comparably, the Mio SLICE does offer more features that its competitors. Yet it’s undeniable that lack of optimisation of both hardware and software marred user experience.

You can purchase the Mio SLICE at $129.95 from Amazon where there’s usually a small discount, great return policy, and free delivery depending on where you reside. In return your purchase helps to offset the costs associated with the running of this site. Thanks for reading!

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