[FEATURE REQUEST] Allow to view PwnMail by holding a GPIO button

[TailsFanLOL]

Is your feature request related to a problem? Please describe.
It's pretty annoying to use the CLI or the web UI to check inbox.

Describe the solution you'd like
When there's a new message, there would be a little "1" icon on the screen (red if the screen is in color), and when you hold a physical button you are able to view last incoming messages just like on a real pager. In the config file, there would be an option to chose the button for that (like GPIO1 or NONE) and/or chose a notification method (none, screen only, LED, beep).

Describe alternatives you've considered
An Android/Ubuntu Touch app with push notifications.

Additional context
None