I see the ad for these all the time- breastfeeding bracelets to keep track of how long you breastfeed, when you breastfed last and for how long. The biggest seller of these that I see is www.milkbands.com.
I never saw the need for these until I have a preemie baby and to really pay attention to how long and when my baby breastfed. Was also useful when I tried to increase my milk supply to know when – and which side-I last pumped on fed baby .
Not sure how they work- but I have a couple of other ideas to try. To remember which side- use a diaper pin or small pi on your bra strap ad transfer to the side you last breastfed on. Can also use a hair elastic on your wrist- make sure its not TOO loose. An expandable bracelet or bangle would serve the same purpose.
Other breastfeeding bracelets:
Nursing bracelets These are ice- you can get in baby’s birth stone- they are quite pretty.