Hi,
Have you purchased sms gateway?
For sending SMS to android device, SMS gateway is required.
I am web developer and have worked on PHP sites to send sms activation code for Account registration and Coupon Code Activation.
You will have to upload your php code on liver server.
As local server are not capable of sending email features.
Let me know, if you really want this work to be done.
It require 5 days to configure a server and 2 days for SMS API setup and 1 day for testing on Android studio.
If you agree, then please send me your code and UI design for the website and app.
Looking forward
thanks
Gurbir