android automatic application restart if device is in homescreen and idle for a period of time

I'm writing an app that w开发者_高级运维ill be used in public transportation and I have a special requirement for it. I need the app to auto restart/bring to front somehow if all the following conditions are met:

-the user presses the back key or the home key and the app is minimized

-a period of time has passed since the device is idle

In conclusion I'd like to know what should I use, broadcast receivers or background services. Code snippets or examples would be appreciated :) Thank you !

You should register a BroadcastReceiver for screen_off action and on it's onReceive() method unlock the screen if required and launch your application.