One of the things I like to do when I’m cycling, is keep track of various statistics related to my ride.

This includes things like speed, cadence (how fast I’m peddling), and heart rate.

To do this, I have a number of sensors that connect to my bike computer (Garmin Edge 810).  The sensors communicate with the bike computer using a low power communication mechanism called ANT+.

There are, however, some advantages of being able to track the sensor data on my iPhone in the various fitness apps (Strava, Endomondo, iBiker, etc).  The problem is that the iPhone needs an adapter to receive the ANT+ signal.  It’s not a big adapter, roughly the size of a charging cable connector.  In addition, the adapter is currently only available for iPhone 4S’s and earlier … it uses the 30 pin connector.  There are no ANT+ adapters for iPhone 5’s & newer (which use the lightning connector).

iPhone 4S’s & newer do have a variation of Bluetooth called “Bluetooth Smart” … also known as Bluetooth Low Energy (BTLE).  SOME fitness sensors support BTLE, but very few support both BTLE and ANT+.

This is where the 4iiii Viiiiva Heart Rate Monitor comes in.  It functions as a heart rate monitor with both ANT+ and BTLE communication.  In addition, it can act as a BRIDGE between other ANT+ sensors and feed the data via BTLE.

The Viiiiva will act as a basic heart rate monitor, broadcasting the data over both ANT+ and BTLE.  This is great if you only want  a single heart rate monitor that will work with both an ANT+ receiving device (like a bike computer) AND a device that can only receive BTLE (like a smartphone with a fitness app).  For this alone,  I find the Viiiiva a useful device.

What’s unique about the Viiiiva is when it’s configured to act as a bridge between ANT+ devices and BTLE receivers.  In this mode the Viiiiva will receive data from various ANT+ sensors and re-transmit the data via BTLE to an iPhone or other compatible device.

In theory this is a great idea … it allows you the flexibility of using sensors compatible with most bike computers with the smartphone apps, without needing a special adapter.  Because ANT+ broadcasts to any device listening, you can use ANT+ sensors with  ANT+ compatible devices AND a BTLE device.

This is great for investment protection.

There is, however, a catch.

The protocol that the Viiiiva uses to broadcast multiple devices over a single Bluetooth connection isn’t supported by most fitness apps.  There are only 3 apps that support the protocol that I’m aware of.  Strava, Endomondo, iBiker, etc, all support BTLE … but not the data coming from the Viiiiva.

The company that develops the Viiiiva have a workaround … of sorts.

If the app that you are connecting to does not support the multi-device protocol, it switches to a round robin mode … where it will connect one of the devices it’s bridging, transmit data, then disconnect and reconnect with the next device it’s bridging.  This goes on for all the devices it’s bridging.

This results in the fitness app thinking that the devices that the Viiiiva isn’t currently transmitting has disconnected.  In fact the Bluetooth icon on the iPhone display actually shows a disconnect and reconnect each time the Viiiiva switches devices.

Below is an example of my cadence on a recent ‘ride’ on my bike trainer using the iBiker app.

Notice how the value drops to zero frequently?

Here is an example of my cadence on another ride, when I was using the ANT+ adapter to receive the data (again using iBiker)…

No dropouts at all … the only dips in the data were from when I actually did slow my pedaling.

I REALLY would like the Viiiiva to work as advertised … and when (if) the fitness app vendors add support for it, I’m sure it will be a boon.  Until the specific multi-device protocol it uses is adopted, it’s just a slightly more expensive ANT+ & BTLE heart rate monitor.