Most persistence of vision projects I have seen involve moving a strip of leds fast enough that our eye perceives it to be an image. Make magazine has covered many projects of this type.
Jens Wunderling, a student of the Digital Media Class at UDK Berlin, has created at second glance, an alternative approach to [...]

Fur, creators of the Painstation and Furminator (among others) have just released information on their project Earworm Assault Devices. From the website:
“Sound is unavoidable (the ear can’t be shut like the eye) and evolutionary hardwired into our cognition apparatus, it can reach into the subconscious and arouse emotions. A well made sound can get stuck [...]