Smartwatches: Specs and reviews for the leading models

As the number of smartwatches on the market continues to grow, a few things are becoming clear.

With many reviews focusing on how long models last between charges, manufacturers are trying to pack in more powerful batteries or find other ways to extend their life.

Recently released models have abandoned the built-in cameras found in Samsung's original devices. Instead heart-rate monitors and ambient light sensors - which adjust the screen's brightness - are becoming preferred components.

There are still several operating systems powering the tech, but many of the leading manufacturers have opted to release watches powered by Google's new Android Wear operating system over recent weeks, suggesting it will become at least one of the dominant options.