Very Simple cross platform Laptop & Mobile Battery Alarm app

I want to make a very simple battery alarm app for all version of windows - windows 11,10,8,7,xp & all types of Linux & Apple Mac on computer and android & iphone ios on mobile phone. It will issue a popup notification in the area of screen as specified by user (for eg A user may want to display notification at the center of screen, another user may want notification at bottom of screen) or when battery will reach level as told by user. User can specify up to 20 notification levels. Notification can be text, audio or video message or all 3.
This app will be a adware. If user does not buys the app he will have to see Ads whenever a alarm will generate. App will download Ads from a web link and show below alarm notification.