5. FINIS’s Swimsense ($200; www.finisinc.com)

Why we like it: If you love using a pool for dropping the pounds, the Swimsense watch is ideal because it does something no other swim watch can do—it knows what type of stroke you’re using while you swim. Why is that important? Certain strokes use more muscles—and burn more calories. As you glide through the water, this gizmo can tell exactly what stroke you’re using, so it can accurately display distance and how many calories you’ve burned—in addition to keeping track of which types of strokes you used during your workout and how fast you were swimming (among many other fitness factors). Once you’re dry, the watch works with a software package that can give you a detailed report on what kind of a workout you had in the pool, so you’ll know what to do to reap even more benefits the next time you dive in.