Responsive Surface Technology (ReST) is taking sleep tracking to its logical conclusion with its smart bed. The ReST bed, which debuted today at CES, features a proprietary smart fabric and sensors to track your sleep habits, and it uses that data to make sure the bed stays comfortable as you toss and turn at night. Within its mattress are 18 air sensors that constantly inflate and deflate based on your preferences -- be it something incredibly firm, or a mattress that's as soft as a cloud. We've already seen smart beds from Sleep Number, but the ReST is going far beyond mere sleep tracking. It's more like an ever-evolving sleep surface. But, as always, sleep comfort doesn't come cheap. The twin ReST smart bed will run you $5,000 when it lands in March, while the queen version will go for $7,000. It's also working on a king version with two independent sensing areas.