One PC at work, another at home, a laptop on the plane, and a personal digital assistant in the taxicab: keeping all that data current and accessible can be a major headache. Randolph Wang, a Princeton University computer scientist, hopes to relieve the pain with one mobile device. Designed to provide anytime, anywhere access to all your files, the device stores some data, but its main job is to wirelessly retrieve files from Internet-connected computers and deliver them to any computer you have access to. Wang's prototype is a PDA with both cellular and Wi-Fi connections, but the key is his software, which grabs and displays the most current data stored on multiple computers. Wang has tested his prototype with more than 40 university and home computers on and around the Princeton campus. He eventually wants to shrink the device down to the size of a wristwatch to make carrying it a snap.