Small remote light switch

I would love to know the smallest, yet economical, way to have 3 LED's turn off WITHOUT having a wired connection.  I want to have a (or several) battery operated LEDs which could be remotely turned on and off by use of radio frequency (garage door opener), sound (The Clapper), magic (David Copperfield), or some as yet unknown method. 1 transmitter would operate all lights simultaneously.  The transmitter could be any size, but the receiving end (the lights) have to be kept small.  What would I have to use to have the smallest solution?  I thought the creative minds here might be able to figure it out.  Any help??