Seen in Magic Mary 27.5 form here, the Schwalbe dual chamber tyres should see a release date sometime in the middle of this year. They will first be released in the trail/all mountain focused treads, but should find their way onto all of Schwalbe's mountain bike offerings.
The first smaller chamber hugs the rim and will be a much higher pressure than the second. The second and bigger chamber will be where traditional tyres would hold all the air. The first chamber's job is to keep the rim safe from hard impacts and prevent pinch flats. It will be able to hold about 5 bar of pressure, maintaining a hardness that will protect the rim from dents, while allowing the second chamber to run significantly less pressure, even compared to tubeless tyres. The bigger, second chamber will be able to run pressures below 1 bar, though that might not be the most efficient with rolling resistance.
Brendan Fairclough and Andrew Neethling were a couple of the riders that were testing out these tyres.