When Pokémon Go Plus finally came out, it just didn't work as players hoped. When the Plus lights up, players can tap the center button to either catch a Pokémon or snag goods from a Pokéstop. Unfortunately, you don't really have a choice about which of these two things you can do; if there's a wild Pokémon nearby, the Plus has to catch it before you can access any Pokéstops. Additionally, the Plus will only use regular Pokéballs and not your fancy high-yield balls, and players report that the catch rate is far lower than what you'd get if you just used the app, leaving many players coming up empty-handed. You also can't use any items that would make Pokémon capture easier.
And that's not all. You'll still need to be running the battery-draining app on your phone, the battery of the Plus is not rechargeable, and it'll constantly disconnect from your phone. You also can't catch types that you haven't already caught. You may as well just use your phone. Or, like, just give up completely.