As advanced as office chairs can be, they're still based on one increasingly bad assumption: that we're sitting upright in front of a traditional computer. Steelcase's upcoming Gesture chair at last acknowledges that we're living in a world of smartphones and tablets. Its back and seat shift in tandem to maintain support in any number of real-world postures, whether it's leaning back to check text messages or curling up for an e-book. The armrests are equally flexible to save us from the added strain that comes from holding a gadget in-han