Apple has launched a celebration of America's national parks, with awards and stickers for Messages inspired by national parks for workout rewards.

On July 15, Apple Watch users that complete a walk, run, or wheelchair workout of 3.5 miles will get the award and the stickers. The distance was selected, as the 3.5 miles matches a hike from Old Faithful to Mallard Lake in Yellowstone National Park.

"America's national parks are an inspiration to us at Apple, and we know they are as important to many of our customers as they are to us," said Apple's CEO Tim Cook. "Our goal is to leave the world better than we found it, so this July we're making it easier for anyone to help preserve the beauty of our natural, cultural and historical treasures."