(Pocket-lint) - Garmin has added a new activity tracker to its line-up, but this time it's strictly for kids.

The Garmin Vivofit Jnr is a fitness tracker designed to encourage children aged from four to nine to keep active, with different fun-looking models that are durable and even swim friendly, thanks to waterproofing.

The tracker also has a one-year battery life so it can be worn 24/7.

It tracks steps, sleep and kids' activities, encouraging them to play for a minimum of 60-minutes each day. There are challenges that can be set, and fun, educational mobile adventures to be undertaken.

The Vivofit Jnr works with a parent-controlled mobile app, so grown-ups can set challenges themselves and offer rewards for meeting them.

"We're excited to announce our first wearable just for kids," said Andrew Silver, Garmin's senior product manager for fitness.

"It was designed with kids and parents in mind, from its durable and comfortable band to its engaging app that motivates kids to get moving, while keeping parents involved."

Coming in several styles, including plain black, broken lava, digi camo, purple strike and real flower patterns, the Vivofit Jnr costs £79.99. The included band fits wrists up to 145mm, while an XL band will be available separately for wrists from 146 to 170mm. Existing Vivofit 3 accessory bands also work with the device.

Writing by Rik Henderson.