A Near-Ultrasound (NUS) Data Link
bunniestudios.com
bunniestudios.com
2 devices with a single LED on each can establish half-duplex wireless communication based on light impulses. I think that is a much more efficient and cheap way to transport configuration settings or even an entire program.
Ultrasonics are a really cool and easy way to have short range transmission of data, or even broadcasting with a loudspeaker. The data rate may be low, but it's perfectly fine for stuff like toggles, or transmission of commands.