Android/IOS application security consulting

We need a consultant to help secure our android and IOS application that handles PHI. Currently we need advice and guidance no actual coding is required. The applications can share information via text & email. They can store backup information so the app can be reinstalled or moved to another device and settings and data can be restored. The apps can also transmit to a hospital picture archiving and communication system (PACS). We need ideas about how to implement secure communications, verify the host device (device running app) is connected to secure wifi, secure backups with encryption and protect data at rest with encryption where applicable.