Test the speed of the WiFi using a computer and a mobile phone (or tablet)
Play your demo on your Android device with the App Demo Player app
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.