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.