i need an aap for a blood bank that sends realtime availability reports to a whatsapp group

I'm looking to build an app for Blood Bank which will be able to send real-time availability reports to a WhatsApp group. This app will be able to integrate with WhatsApp, and will have Blood Donor Registration features. It will be built to work on both Android and iOS platforms and I am open to suggestions in terms of the design. The deliverable of this project is a working mobile application on both Android and iOS platforms.