The ability to connect with your clients and keep track of their progress. It's easy to use, it has a great interface, and the customer support team is very helpful. I love that I can send my client reminders about their next session and set up automatic payments through Stripe or PayPal. It would be nice if there was more integration with other apps such as Runkeeper. There are some features that I wish were better integrated into the app. For example, I'd like to be able to see what my clients have done in the past week without having to go back to the website. That being said, the overall experience is really good. I'm using fitapp.pro for my personal training business. I've been able to easily manage all of my clients' sessions and have them pay me directly through PayPal or Stripe.