MP3 players fulfill many roles for the people who use them. For some, a portable audio device is true to form as an essential commuter companion; others turn their players into home audio systems by attaching them to speakers. But one of the most popular uses for an MP3 player is as a workout motivator, which is why companies have packed fitness-friendly extras into the devices over the years. The most recent example is found in the Haier America Trainer, a 2GB player with a surfeit of features aimed at getting you in shape. At $60, the Trainer is a solid investment for gym rats who want to get the absolute most out of an MP3 player.