Singletrackworld.com:

One for you commuters out there (and for both of you fixed gear offroaders) is this ‘two speeds on a single sprocket’ fixed wheel sprocket. We’ve not counted teeth, but it could, for example, have a 17t and a 19t on the same body, allowing fixed wheelers (especially those who don’t run a rear brake) to have two gears. A ’start of week’ and ‘end of week’ easier gear for messengers. Or a ‘riding to the trail’ and ‘riding the trail’ gear.

It should be out later in the year. Keep your eyes on www.surlybikes.com for more.