At first glance this looks like the ubiquitous "will return" sign, but then you realize the secondhand is moving. Hey, wait a minute. This is a clock that runs on two AA batteries. Set it ahead 15 minutes and leave it on your door, and then if seeing is believing, you will always be back 15 minutes from now.
This may be the solution to the unified theory that Einstein was looking for. Or perhaps it will tear a hole in the time/space continuum. Could be dangerous. Try your luck for $12.