Is there a way for me to show a customized message on the lock screen?

I'm using DevicePolicyManager to make an app that can lock devices and was wonde开发者_C百科ring if there was a way to show a custom message on the lock screen if I lock the device with DevicePolicyManager.

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There should be a way to show some kind of Activity above the Log-Screen (like the Winamp-App does it).

I found the FLAG_SHOW_WHEN_LOCKED-flag which seams to do just that.

Also, I found this recourse which illustrates how this works.