What would i need to develop an Ivr system?

IVR=Integrated Voice Response -- systems typically used by call centers, you know the annoying ones that talk to you to tell you what your menu options are, tell you to hold, etc. These systems help with staffing by helping you route calls and by avoiding the need to have someone available to answer each call the moment it arrives. There are packaged solutions available, so you probably do not need to develop your own.