When you work in an more agile way you end up writing a lot on post-it notes (stories, tasks, random thoughts, etc.).
Wouldn’t it be awesome to have post-it like notes that are made of the same material as a white-board? That way you could wipe the content of the note after you don’t need it anymore and write some new and great idea on it.
As a bonus they would not use glue to stick to the surface, but they would be electrically charged (static electricity mind you) so that you could stick them on almost any surface.