How to make a custom bluetooth 4.0 module

Where can I go to learn about making a custom bluetooth 4.0 transceiver device for Arduino that would transmit data to an iOS/Android device. I plan on making a custom app for both platforms that would display the data. Buying a ready made module will not work since it needs to be a specific shape and I would like to include every component of my project on a single PCB board. Any tips or suggestions would be greatly appreciated.