Hi in first a'm sorry for my English
I download and instal calendar application of play store and i need only display this app or widget in my write application in panel activity i mean:
you can start another app from your app. But you cant force the user to go back to your app after a specific time. It is the decision of the user which app he want to use. Or which app he want to quit/stop.
Ok, maybe using a timer in a service you can start your activity. But this will be irritating to the user i guess if a app pops up unexpected.
If this will happen on MY device i would remove that popping app ASAP.