Tools for tracking and fine-tuning our fitness regimens are more abundant today than ever. And they're getting smarter, too. From the simplicity of mechanical step counters to ultra-smart digital devices that pack accelerometers and GPS radios to follow our every move, it's clear the wearable category has grown. These devices now collect data, provide a soundtrack, prod us when we're lazy and reward us when we've achieved our goals. They've also considerably scaled down in size, so we no longer resemble gadget-laden test subjects when tracking our workouts. In fact, wearables have become rather stylish. Join us in the gallery below then as we take a brief look at the evolution of the activity tracker.