Keykeriki is the first open source 27Mhz wireless keyboard sniffer. Inside this compressed archive a hardware tarball, a software tarball, and slides from ph-neutral are all included.
You can download it from the following link: https://packetstormsecurity.com/files/download/78433/keykeriki.tgz
Source: https://packetstormsecurity.com/files/78433/Keykeriki-Wireless-Keyboard-Sniffer.html