Over on YouTube user Samy Kamkar has uploaded a video showing how he was able to use an RTL-SDR to copy his friends wireless doorbell signal and prank him by replaying it using an Arduino and 433 MHz transmitter. His video goes through the entire reverse engineering process he used from recording the wireless doorbell signal with the RTL-SDR, to analyzing and understanding the signal and finally to programming the Arduino with the code to replicate the doorbell signal. If you don’t like video explanations, Samy has also done a write up of the same material on his website.