Fitbit Alta HR
The newest Fitbit is the best one: it packs heart rate on a small band, and has plenty of designs as well as styles. Just don't wear it swimming, because it's only splash resistant.
Fitbit Flex 2
The Fitbit Flex 2, on the other hand, is waterproof. And it can be worn with bands, jewelry accessories or pendants, like this one.
Fitbit Charge 2
Fitbit is currently our favorite fitness-tracking platform. The Charge 2 adds better controls for timing runs and workouts, but doesn't have GPS.
If you're getting a gift for a runner, Garmin's GPS watch is the pick. It's also waterproof for swimming, and tracks heart rate. Its battery life lasts a couple of weeks, too.
Apple Watch Series 2
The best smartwatch at the moment, Apple's swim-ready, GPS-equipped Apple Watch Series 2 also has a speakerphone, Apple Pay and works with plenty of strap accessories. But you still need an iPhone to use it.
Apple Watch Series 1
Spend a little less, and the Series 1 offers just about everything the Series 2 has, minus GPS and swimproofing. It's a great everyday pick.
Samsung Gear S3
The flashiest and splashiest smartwatch, Samsung's Gear S3 has optional standalone LTE phone modes in some models, and a design that looks like a real (but big) sports watch. It works with the iPhone as well as Android phones, but runs its own limited apps.
Huawei Watch 2
For Android phone owners, the best Android Wear-ready watch running Google's software might be Huawei Watch 2. It also has GPS, Android Pay and always-on heart rate for workout-tracking.