It is a android app demo which reads data and plots the data in a world map. It is written in Kotlin. You can change the data source url to your own server. Therefore, it is quite easy to modify it to treading covid-19 heatmap or any other heatmap.
The underlying method inthe project is quite simple. It just a webview in android which display a locla html file. The html file contains JavaScript code which reads data and plot data in a world map (using plotly).