Test the speed of the WiFi using two Android-based devices
You can send this file to other people by email for example.
Or you can host the demo on your own web site.
Use a screen recording software to create an app demo video.
Step by step guide to video recording: How to create an app demo video.
Print your demo storyboard: Print to PDF
Step by step guide to PDF printing: How to print a Demo to PDF.
Build a native Android app and export it to APK.
Step by step guide to APK creation: How to build a native Android demo app.