Similar to:
http://stackoverflow.com/questions/3381594/how-to-make-android-activity-show-above-keypad-screen-lock
How can I display an Activity or Dialog over visible lock screen?
I have already tried displaying my lock activity when screen goes on setting various window type in Activity.onCreate() method:
TYPE_PRIORITY_PHONE
TYPE_SYSTEM_ALERT
TYPE_KEYGUARD
and others
together with SYSTEM_ALERT_WINDOW and INTERNAL_SYSTEM_WINDOW permissions.
My activity is visible after I unlock the device.
UPDATE:
I actually already managed to display my own Activity instead of default lock screen. It work perfectly unless you use HOME button.