If you find the alert dialog appearing every time you plug Lumu Power in your device annoying, here's how to disable it.
Open Settings by tapping the gear icon in the top left corner.
Tap the 'GENERAL SETTINGS' button and you will arrive at the next screen. Make sure your Lumu Power is plugged into your device, otherwise you will not see this setting. Uncheck the 'AUTO APP OPEN' setting as seen in the picture.
The next time you plug in your Lumu Power, you won't see the dialog box again.