Hello guys, my question is about developing VOIP application

am student computing, and am about to prepare my first project which is creating an application using programming
the application am aiming to develop is VOIP from pc to mobile and the contrary
so wht am asking you guys is to give me ur thoughts and ideas and help me by ur suggestions coz i wanna add new option(s) tht can be useful in VOIP applications
i will be so thankful if u can guys help me out with ur brilliant minds