Your iPhone is immensely distracting. It doesn't matter what you do for a living and how diligent you are, it is likely that, at some point in your day, you are wasting at least some volume of time using your phone instead of working. GoWork attempts to help people who have this problem by gently "reminding" them to get back to work after a certain amount of time. While it works to some degree, it is fairly limited in many ways.
The concept is very basic. Set a time frame for how long you are allowed to distract yourself on your phone. Then choose or add new messages to the app that will be used to remind you. You can even turn on persistent notifications so that if you ignore the first one, the app will keep harassing you until you in fact stop doing whatever it is you are doing and get back to work. This all works quite well, but without additional features, any way to define when it is okay to interrupt you and when it is not (persistent notifications while on the phone would be a problem), or other options, it has limited uses.
For times when you are playing a game when you should be working, GoWork is a great tool to have. While it won't provide quite the degree of control you might like over something that will notify you repeatedly until you respond, it is a very good idea and hopefully we will see some feature upgrades in the future that make it even more efficient in keeping users on task.