Flutter or Android App Developer

I'm seeking an experienced Flutter or Android app developer to implement a specific functionality in a mobile application.
Project Goal: I need to enable communication between two apps via close-range interaction (similar to NFC, but without the need for physical tags or external devices).
App A (on a customer's phone) should automatically emit a user ID when brought close to a POS device.
App B (on the POS device) should detect and receive this user ID from App A.
Think of it as one app (App A) acting as a transmitter, and the other (App B) as a receiver, triggered by proximity — all through software.
If you have experience with similar technologies (e.g., NFC emulation, Bluetooth Low Energy, Wi-Fi Direct, or other proximity-based communication protocols), please reach out with your portfolio and a brief outline of how you would approach this.
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