4iiii Viiiiva Heart Rate Monitor Review

The 4iiii Viiiiva is an accurate heart rate monitor with a neat trick—it can bridge ANT+ to Bluetooth devices

4iiii Viiiiva Heart Rate Monitor
(Image: © Nick Harris-Fry / Future)

Our Verdict

The 4iiii Viiiiva heart rate monitor is good value and has proved accurate throughout more than 30 hours of testing. It can also store workout data, including swims, and bridge ANT+ to Bluetooth devices, which will be invaluable for those still using older ANT+-only sensors.


  • Accurate tracking
  • Bridging feature
  • Workout storage
  • Swim-proof


  • Short battery life
  • Only one Bluetooth connection
  • So many iiiiiiiis

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The combination of value and accuracy makes the 4iiii Viiiiva one of the best heart rate monitors, and it goes above and beyond with a clever bridging feature, which transmits ANT+ signals from other devices through a Bluetooth connection.

While its battery life is subpar compared with newer devices, the 4iiii Viiiiva is still worth considering as one of the best cheap heart rate monitors, even if you don’t need the bridging feature.

4iiii Viiiiva Heart Rate Monitor: Price And Availability

The 4iiii Viiiiva originally launched in 2012 and it is testament to the quality of the monitor that you can still buy it today. The price has dropped in that time and the list price of the 4iiii Viiiiva is now $49.99/£49.99.

How I Tested This Heart Rate Monitor

I have been wearing the 4iiii Viiiiva to track my workouts for several weeks, either by itself or at the same time as wearing the Polar H10 chest strap to check the Viiiiva’s accuracy. I have used it mostly for running, along with a couple of strength sessions.


4iiii Viiiiva Heart Rate Monitor

(Image credit: Nick Harris-Fry / Future)

The 4iiii Viiiiva is a lightweight sensor with a plastic main unit that clips into an adjustable fabric strap, with the pod acting as the fastener for the strap. The sensor uses a CR2032 battery and connects to other devices through both Bluetooth and ANT+. It can only support one Bluetooth connection at a time, whereas many heart rate straps can now support two or three.

Once the sensor is clipped into place it’s easy to pair it to another device, though you don’t get any sound or light signal from the pod itself to indicate it’s connected. The strap can be adjusted from 23in to 52in (57-132cm) and I found once you set the desired length it stays in place reliably and comfortably during long workouts.

The Viiiiva has an IPX7 waterproof rating and can be used to track your heart rate during swimming since it is waterproof to depths of 3m and can store workout data in its internal memory to download later. 

The internal storage can log up to 65 hours of heart rate data in .fit files you can download from the partner app. If you connect other sensors like power meters to the Viiiiva it will record that data too (though this reduces the number of hours it can store), which makes it a handy back-up in case your watch or bike computer crashes or runs out of battery during a workout.

4iiii Viiiiva Heart rate monitor front

(Image credit: Nick Harris-Fry / Future)

Sports Performance

For all its clever tricks the 4iiii Viiiiva wouldn’t be much use if it wasn’t an accurate heart rate monitor, so I’m happy to report it has been flawless throughout my testing. It reliably logged the same heart rate as the Polar H10, which I have found to be the most accurate HRM available through years of testing.

I did several hard interval runs wearing both the 4iiii Viiiiva and the Polar H10 connected to different watches. Both during the sessions and when looking at the heart rate graph afterward, I did not see any differences in the readings of the two HRMs.

During the weeks I used the 4iiii Viiiiva I was able to link it to a variety of watches and apps easily, though the fact it only connects to one Bluetooth device at a time meant I had to disconnect it from one to link it to another. It also means if you’re using the Viiiiva with a Bluetooth-only sports watch and Zwift on a Bluetooth-only device at the same time, only the watch or Zwift can show your heart rate.

ANT+ Bridging Feature

While ANT+ bridging is not a feature I need, it’s something that will be invaluable to some and it’s the chief reason to choose the 4iiii Viiiiva over other heart rate monitors.

To use the feature, connect the 4iiii Viiiiva to the partner app, link ANT+ devices to the heart rate monitor in there and then broadcast to an external device. 

When the 4iiii Viiiiva originally launched, its ability to link ANT+ devices to Bluetooth ones was a much bigger deal. Since then Bluetooth connectivity has become a standard feature on sports sensors.

However, the bridging feature still has its uses, notably for anyone with an older sensor or indoor bike trainer that uses ANT+ only. One other use for the bridging feature is that it can bundle several ANT+ signals up into one Bluetooth signal, which is useful when connecting to Zwift or other apps on a device that can handle only two Bluetooth signals, such as Apple TV.

Battery Life

4iiii says the Viiiiva will last up to 160 hours on one battery, which is significantly less than most HRMs that use coin batteries. The Polar H10 lasts 400 hours on a coin battery, for example, and the Wahoo TICKR lasts 500.

I found the battery drained faster than this 160-hour estimate. You can see the battery life of your device in the partner app and mine has dropped to 64% after around 30-40 hours of use.

4iiii Viiiiva Heart Rate Monitor back

(Image credit: Nick Harris-Fry / Future)

Is The 4iiii Viiiiva Worth It?

The 4iiii Viiiiva is an accurate heart rate monitor at a great price and if you have a use for the bridging feature then buy it. If not, you can get accurate heart rate monitors for less, such as the Coospo H9Z, which has a rechargeable battery and can handle two Bluetooth connections at once, though it can’t store workouts or track swimming.

If you upgrade to more expensive models such as the Polar H10 and Garmin HRM-Pro Plus you get longer battery life and more comfortable straps, and some extra features like running technique stats on the Garmin, but you don’t get a more accurate device for your money.

Nick Harris-Fry
Senior writer

Nick Harris-Fry is a journalist who has been covering health and fitness since 2015. Nick is an avid runner, covering 70-110km a week, which gives him ample opportunity to test a wide range of running shoes and running gear. He is also the chief tester for fitness trackers and running watches, treadmills and exercise bikes, and workout headphones.