Using ANT+ accessories in the iWorld
No iOS device has native ANT+ communication support built in. For the iPhone 4 &amp; 4s, Wahoo makes a 30 pin ANT+ dongle. Newer devices can also utilize this dongle with a 30 pin to Lightning adapter.

http://www.wahoofitness.com/devices/wahoo-key-16.html

Once your setup with the ANT+ dongle, you'll need a 3rd party app to read the data. Some, like Strava, can push data to the iOS Health app:

https://support.strava.com/hc/en-us/articles/216917527-Health-App-Integration-iPhone