Originally it they said it didn't.
When the Pokemon Go Plus band was announced there were a couple of caveats along with it. It wouldn’t provide an alert for any Pokemon attracted by Incence and that the band wouldn’t track distance walked while running in the background.
Turns out it actually does. Nintendo has now updated it’s information page on the device and confirms;
Correction (14/9/2016): Even while Pokémon GO is operating in the background, distance walked is applied towards hatching eggs and Candy earned for Buddy Pokémon.
The news first broke when a Reddit user got their wrists on the device early and confirmed it. Either Niantic didn’t tell Nintendo they changed the software to do so or yeah we don’t know.
Does this change your opinion the Go Plus band?
It's Black, Back Again.
If these aren't the coolest graphics...
Loco Motive, MySims: Cozy Bundle, Stray, Nine Souls, Servonauts.