Have you ever used an app to help with your stutter?

Have you ever used an app to help with your stutter? If so, did you think it was useful? What type of features would you like to see in an app for stuttering? We are developing an app right now which will come out in April 2020 and will be free! Half of our team are people who stutter and they have given a lot of valuable input but they can't speak for everyone. So please, tell me what you would want from an app and I will let you know once it's launched so you can try it out.