Of the nation's four biggest wireless carriers, only T-Mobile USA has revealed plans to deploy Passpoint, a technology that would allow wireless users to automatically access Wi-Fi hotspots from carriers' 3G and 4G cellular networks. Certification of Passpoint on network gear and end-user devices, such as smartphones and tablets, begins in June, according to the Wi-Fi Alliance, which coordinated development of Passpoint , based on the Hotstop 2.0 specification, over the past two years.