Replying to Invention Convention Help

All right here's the thing: I have to come up with an idea for an invention for a science fair at my school, and I could use a little help. My current idea is a backscratcher that applies cream to your back/body part while it scratches, so you get the satisfaction of scratching, while healing whatever rash or itch you are encountering at the time. Not really sure it's the best so I decided maybe you guys could provide some ideas.