Niantic Labs will soon ship an update for Pokémon Go that will add the new Buddy Pokémon feature. After having updated the game, players can choose a Buddy Pokémon from any of the Pokémon in their collection. The Buddy will then bring the player in-game rewards. This could be, for example, a certain amount of candies for walking a particular distance with the buddy selected.
Technical support for the soon-to-be-sold Pokémon Go Plus is also included, and apparently Niantic has also removed support for jailbroken smartphones (which is no doubt going to affect a fair few people). The update will hit App Store and Google Play Store in North America and other territories soon.