433 MHz Key retranslator via internet and some hardware
Code examples:
index.php - Server for keystorage
MainActivity.java - Android application for communication between keystorage server and key transmitter via bluetooth
garage_key_transmit.ino - Arduino sketch for key with transmitter
garage_key_receive.ino - Arduino sketch for reading from original key
Alternative way for offline functionality from our friend, Dmotriy Murzinov: http://idoka.ru/blog/posts/keeloq-protocol-simple-cloning/ - a little more work, but you don't need an internet for this solution.