The Pokémon Go Plus is a wearable that works with the game to help you find and catch Pokémon in the Pokémon Go augmented reality. From what I gather, the wearable will track your position (probably through GPS or more likely via Bluetooth while paired with your phone) and when you come near a Pokémon it will vibrate in order to notify you that the Pokémon is nearby and ready to be caught. Rather than keeping your phone out and screen on you can wait for the notification from the Go Plus before needing to pull out the phone.
The release date is now listed as December 31, 2016 but based off the recent news stating that the game would become available some time in July, I would assume that this is just a placeholder until a firm release date is available.
Roy likes to dabble in all things Android and contributes everywhere he can. He owns the site rwilco12.com and its accompanying forum, he develops his own apps and ROM’s, is a Moderator and Recognized Developer on XDA-Developers.com and is the VP of Public Relations for AndroidFileHost.com.