The Hug-time Bracelets are watch-timer like bracelets that Trolls wear as they allow them to know when it is "hug time". They hug ever hour, until Queen Poppy decreed that hug time can be "all the time". Branch is the only Troll that doesn't wear one, as he didn't do hugs.
The bracelets blow into a flower, glows and makes a "ding" sound when it is time to hug. The ding allowed Poppy and Branch to find the captured Trolls in Bergen Town's castle and to bring a little music to True Colors. Bridget was listening to the chiming dings of the bracelets - from the outside of the "pod" that they were kept in -, before Chef got her to bring the Trolls to the castle's dinning room.