You know the problem: There you are in the bath, trying to read a book. One hand is dry, the other wet and not suitable for touching pages. The book is floppy and will not stay open, But lo, you have printed a Page Opener and stuck it on your thumb. Now you can keep the pages spread for easy reading, and still manipulate the book to turn the pages one-handed. (Book credit: The Diamond Age, Neal Stephenson)
Scale this to suit the size of your thumb. I have short, fat fingers.