The Denman Shower Brush (around €5) had me seven kinds of confused when I saw it in Boots, so of course I had to bring one home to investigate. It's a small, circular handheld brush with evenly spaced plastic pins of uniform length, and according to the blurb allows you to "enjoy an invigorating massage every time you wash your hair." Apparently the Shower Brush is to be used for applying shampoo and the like, and the models on the packaging certainly look like it's enhancing their shower experience, with their super sudsy hair.
Honestly, though, I can't imagine using it to massage in shampoo - the extra lather would hardly be worth the inevitable mess of knots - although it actually does a great job of ensuring that my conditioner and Moroccanoil are more evenly distributed than I can manage with my hands, and it's way better than the wide-toothed comb I usually use for detangling wet hair with total ease.
Denman's Shower Brush has also totally done away with any desire to try the Tangle Teezer, which gets rave reviews but has always seemed expensive to me. Now, Denman obviously aren't positioning this product as a competitor to the Tangle Teezer and it didn't perform well on my dry hair at all, causing dreadful static.
However, since I only have a problem with knots and tangles when my hair's wet, I'm well pleased with this cheap but effective addition to my kit!