There's more than one way to make a wireless MP3 player, and building it directly into a set of headphones may seem like the easy way out, but it gets the job done. Plus, there are none of those audio-fidelity issues you might run into with technologies such as RF and Bluetooth, which is probably why Sony elected to take this route with its new W-Series Walkman. This 2GB MP3 player is built into a set of impressively small earbud-style headphones and sports a palatable price tag of just . We've got to give props to Sony for the design of the W-Series Walkman, which is available in a choice of two colors (black or pink). Two rectangular audio modules--measuring roughly 2-inches long by 0.8-inch wide and 0.4-inch deep--attach to one another via a flexible, twisting neckband. It's the smallest all-in-one MP3 player/headphone we've ever seen, and it's impressively lightweight, as well (1.3 ounces). Of course, with any such device made specifically for active pursuits, a secure fit is a chief concern. Luckily, the W-Series Walkman is up for the task: we tested the player walking, jogging, and doing jumping jacks and found it quite capable of staying in place during all of these activities. Still, comfort is somewhat of a concern--the fact that the earbuds are integrated will no doubt cause issues for some, despite Sony's inclusion of three sizes of silicone eartips.