Mobile app for construction start up

I am looking to develop a mobile app for a construction start up. It needs to be developed for iOS and include a Communication Tool, as well as specific designs that I have in mind. I am very specific about the design of the app, and need a freelancer who is able to implement my requested features while adhering to my pre-specified designs. Working with me on this project will require the ability to communicate quickly and effectively about the project, as well as knowledge around iOS mobile application development.