It’s possible to buy LED conversions for old-skool 6″ round headlights, like on LR Defenders, but I’m pretty sure it’s impossible to find LED replacement ‘bulbs’ for existing halogen units that work, because there isn’t a high enough output emitter available and they need specially designed reflectors and lenses to give a correct beam pattern for dip and main.
Have a look at cars with full LED headlight units, like Seat Leon, Citroen DS3, Vauxhall Astra and Mokka, and high-end Audi, you’ll see a bunch of small individual lenses, each with its own emitter, matrix units allow the lights to alter beam patterns on the fly, some are even gps-linked, to alter light patterns according to the actual road contours.
Audi even has a laser light system on the latest R8, but they’re all specific to each car model, and I’m confident none could be adapted to any other vehicle.