Aimed at high-altitude trail runners, climbers, and hikers, the water-resistant Ambit houses an accelerometer as well as a host of features like a 3D compass and an altimeter in its rugged composite case. Its GPS locked in instantly in all locales, and its graphical display provided fast feedback. We loved the Ambit's 50-hour battery life and training-specific functions like a recovery-time calculator. Hardcore backcountry adventurers should wear it; for anyone else, it's overkill. [From $500;]