This is a good way to improve vocal skills but I won't call this a communication as we are talking with the computer and there is no one on the other side to hear what we are speaking. This might create an illusion that we can talk in an effective way but I believe that we should always talk with the real person because we get to understand his expressions or even his real-time response for every sentence that we speak. Since English is not my native language, I am using the app called Opentalk and I have found it useful for the above-mentioned purpose.