A general purpose radio frequency transmitter for Raspberry Pi which doesn't require any other hardware unless filter to avoid intererence. It can handle frequencies from 5 KHz up to 1500 MHz. Plug a wire into GPIO pin 4 (hardware pin 7) and it'll broadcast just about whatever you tell it to. Has an installation script. It's recommended that you use a bandpass filter to minimize noise on the air. Works with just about every RasPi (except the B). Has a text based menu to control it. Defaults to 434 MHz (international free ISM band). You can even broadcast spectrogram pictures! Can even do POCSAG to activate pagers!

Pi-based FM Number Station w/ basic Speech Synthesis.