To start, they must offer iPhone and Watch apps that allow you to track your stats, see what classes they offer and log in at the gym. They must also accept Apple Pay so that you can use your Apple Watch (or iPhone, if you brought it with you) to pay for stuff at the gym.
However, the centerpiece of Apple Watch Connected is an "Earn with Watch" incentive program that will allow you to get rewards for using your Apple Watch. At Orangetheory, for instance, you'll be able to score Apple and Nike gift cards by hitting specific goals. Crunch, meanwhile, will allow you to get up to $300 over two years off your membership fees.
If it makes sense for a chain, Apple is also asking them to offer machines with GymKit support. If you've not encountered a GymKit machine before, they allow your Apple Watch to get more accurate data on your indoor workouts by syncing with them over Bluetooth and NFC.
It will likely take a while before you can take advantage of the Connected program at your local gym. Basecamp is launching the program at all six of its clubs. YMCA is first rolling out the program to its St. Paul Midway location before bringing it to 21 other Twin Cities clubs over the next couple of weeks. Both Crunch Fitness and Orangetheory are starting with two locations each in Manhattan. The three latter clubs plan to expand the availability of Apple Watch Connect nationwide throughout 2020.
For Apple, this new program makes a lot of sense. The Apple Watch is already a favorite among exercise enthusiasts. By working with companies like Basecamp to make it the go-to fitness tracker at gyms, the company strengthens its already-dominant position in the wearable space.