Silicone scalp brushes are all the rage in the shower, used to stimulate and exfoliate the scalp increasing blood flow to the follicles. Some claim this helps with hair growth.
They have soft silicone bristles that massage the scalp and help to loosen build up and buff away dry and flaky skin. If you have a sensitive scalp, they can be gentler than using your nails to scrub in your products, or to scratch that annoying itch.
I like to use mine on wet hair to clean my scalp when shampooing then massage in my conditioner. Be careful though they are so relaxing you are bound to waste a lot of water.