At a recent FCC workshop in Washington, disability advocates demanded that government do more to increase the accessibility of the Internet and broadband devices, especially mobile phones. Congressman Ed Markey, a Massachusetts Democrat and former chairman of the House’s Internet subcommittee, has championed such legislation. But for all the hand-wringing about a “digital divide” separating the disabled from the able-bodied, a new era of empowerment is dawning—the result not of Washington’s laws but of Silicon Valley’s technological dynamism. . . .