IPhone : Can an app be automatically opened for short period of time on screen unlock?

I am trying to figure out if it's possible to have an app automatically come to foreground whenever the iOS device is unlocked. The app would simply speak a message. I understand that the app must be already running prior to the phone locking, and my intention would be that the app is purposefully 'activated' to perform this action on unlock, and can also be deactivated (or simply quit).

It's not an app that tracks a user, VOIP, bluetooth, etc. which, from reading the docs, makes me think that it's not possible.