Apple Insider lays out the details on this Financial Times post [Paywall].

The Financial Times said that the developers are “handpicked” by Apple, and under surveillance by security guards while they work. To prevent photos of the labs from emerging, participants are asked to cover up the cameras on their iPhones. Each person is required to sign a non-disclosure agreement.

Developing for the Apple Watch without an actual watch to test on is a challenge. There are a limited number of watches in the wild, certainly not enough to seed all the developers with projects in the works. Visiting the lab is the next best thing if you want to get your app in the store for opening day.