The Transport for London website now offers live data telling you when buses will be departing any London bus stop. As a tool, it becomes particularly powerful on smart phones, allowing you to judge whether to wait for a bus, find an alternative or do something better with your time and come back in ten minutes. As Diamond Geezer says:
This isn't just useful, it's a game-changer for public transport access in London. Now every bus stop has a Countdown display, even if you can only see it virtually, allowing optimal decision making and on-the-hoof journey planning.