Elevator Hacking: From The Pit To The Penthouse by Deviant Ollam and Howard Payne https://www.youtube.com/watch?v=rOzrJjdZDRQ
They've done several iterations of this, including a censored/shorter version for DEFCON 22. This version is the best, with all details, no secrets withheld. I find the content rather stunning, and I've even watched it several times.