I have been using a Bi-Xenon H4 headlamp HID conversion in my B..W for 3 years. It switches instantly from dip to main by means of an elctromagnetic device on the back. It was supplied by hids4u. It is simply the best thing I have done to the bike. It gives superb lighting(much better than the 100W xenon bulb it replaced) and only consumes 35W after 'striking'. Definitely recommend it to anybody! Also very simple to fit as long as you have space for the ballast.
Bill
Bill