"SwingSign" is a app of a sign(message) board which can show a sign you designed in midair virtually three times as large as iPad's display size by swinging iPad sideways.
First of all, SEE the DEMO VIDEO at the support site using the URL link below or by seaching YouTube using keywords "SwingSign Demo English".
This can be used for a concert or a sports event etc.
"How does it work?" is below.
You swing your iPad sideways keeping constat tempo, then the App synchronizing with the tempo, moves a showing part of the sign in the opposite direction of your swing.
So, as afterimage, the large sign seems to have stopped in midair.