Integration between platforms & IoT feature

We are building rental platform. Project is established, phase 1 already rolled out. Before enter to phase 2, we need to add on some features which can be developed parallelly. We need extra helper to add the features. Feature 1: Integration between 2 platforms. To create a new screen to gather users' input and call another platform's API to pass the data. Platform 1=.Net Core. Platform 2= PHP
Feature 2: To integrate an IoT device, SDK ready. To be built in mobile app, Flutter.