You can move your Pokémon GO Plus device to any compatible smartphone. After pairing the device with the new smartphone, it will no longer communicate with your old one. Before moving, it is recommended that you first install the Pokémon GO app on the new smartphone.
For more information, please visit Pokémon GO support at: https://niantic.helpshift.com/a/pokemon-go/?p=web. Note: this link takes you to a web page not created or maintained by the Pokémon Company International.