App developer needed

Real time mobile application that controls an end Arduino (esp8266) device
and shows live push notifications that are sent from the device (IOT).
Supported mobiles: Iphone and Android.
Hardware (of device) is out of scope.
Mobile application UX wireframes will be provided.
Required scale: at least 10K end users on the 1st phase with the ability to scale up if needed.
Minimal bandwidth and payload should be used