Very very nice that you provide a GUI installer.
Could you please improve it to have a self explanatory name like "Emteria Android Raspberry Pi Installer"?
Would be also nice if you could actually start it from the UI and if the app would do all image downloading etc. as the unprivileged user and only do the final writing to the SD card as root? This is kind of common practice to reduce the amount of code that runs under root. Integrating the "Grant access to app X to write to SD card" dialog would be also nice.
And finally, signing the app will allow it to run without a security warning.