GreenTheory is a free iPhone app developed by Theory Holding SPA, falling under the Lifestyle category with a focus on Health & Fitness. The app's main features include obtaining a subscription plan at one of their centers, signing up within the app with your details, and then using a QR code at the desk to activate your subscription and start your workouts.

GreenTheory simplifies the process of getting started with your fitness journey by providing a seamless way to join their program through the app. With a user-friendly interface and the convenience of using a QR code for activation, it offers a straightforward approach to accessing their services.