A few useless items that I know of and in my opinion that are totally useless for babies is the thing you put over a babies penis called a T Pee that prevents the baby boy from peeing on the person changing the diaper.
You can just as easily put a new diaper over the babies penis or even a cloth to prevent getting peed on.
Another useless item is a monitor that you put on your babies leg that attaches to the internet and your smart phone to keep an eye on your baby. You should be watching your baby often enough that the monitor should not be needed.
And last on the list of useless items is disposable diapers that have prints and cartoon characters on them.
The diapers themselves are not useless but the prints on the diapers are useless and just a way to market towards children while they're still young.
Those pictures cost money to print on the diapers and the diaper company has to pay a license fee to Disney or Sesame Street to legally print those characters on the diapers.
The cost of the license is passed onto the parents who buy those printed diapers.
You can buy much cheaper disposable diapers that are plain white without any cartoon characters on the diapers so you'd save some money.