When Apple previewed watchOS 4, the company also talked about an upcoming feature for gym members: GymKit, which would be able to sync your Apple Watch to upcoming models of treadmills and other fitness equipment.

A few months later, and we're at last seeing GymKit in action: Scott Stein at CNET took his Apple Watch for a whirl in NYC gym Life Time Athletic at Sky, currently the only place in North America to support the emerging technology.

GymKit works with a simple tap-to-pair process: Tapping a ready piece of equipment starts the process, and the Apple Watch brings up a confirmation screen. With treadmills, it asks if you want to record a walk or a run. From there, everything on the Apple Watch and the fitness machine's readout are synced: heart rate, pace, active and total calorie estimates, and machine-specific data such as elevation and flights of stairs climbed. Connecting your watch also means the machine shows calorie estimates calculated from your own height and weight data on Apple Health, without adding any extra setup steps on the machine.

Stein has a great overview on how GymKit works, as well as its (very limited) availability:

Life Time Athletic at Sky in Manhattan is the first gym in which machines have been upgraded to work with GymKit: TechnoGym ellipticals, treadmills, stationary bikes and stair-climbers will work, and currently there are 13 machines that are GymKit-enabled. Life Time plans to expand to 130 other locations over time, starting next year with locations opened in 2017, but don't expect to find a GymKit-ready gym around the corner immediately. And, of course, it's unclear how many other fitness clubs will make the move to upgrade for GymKit.

Equinox is expected to have GymKit locations in 2018 using Life Fitness equipment, with a new New York City location being the first early next year. In Australia, five Fitness First centers will be GymKit-ready.

Check out the full experience over at CNET.