Apple is working on interchangeable AirPod headphones that come with health tracking features to measure heart rate and stress levels.

That's according to a new patent filed by the firm which reveals how a new version of its wireless in-ear headphones would be able to fit in either ear.

The filing shows the device slipping into the ear canal and being held in place with a bendable band. 

Apple's current wireless AirPods were first launched in 2016, although some users have complained they can easily fall out or become uncomfortable.

Apple removed the headphone jack from its iPhone models from the iPhone 7 onwards, forcing users to buy wireless headphones.

While Apple users may be hoping for a...