Pokémon has released that Pokémon GO Plus will be available on September 16!
From Pokémon:
The Pokémon GO Plus is a small device that lets you enjoy Pokémon GO while you’re on the move and not looking at your smartphone. The device connects to a smartphone via Bluetooth low energy and notifies you about events in the game—such as the appearance of a Pokémon nearby—using an LED and vibration.
You can learn more about it by visiting Pokémon’s website!