suppose i make an app only for root devices , which will allow to replace the lock screen (the screen that appears when the device's screen is being awaken) .
i know that there are ways to do so without root , but they are all considered a workaround and on some devices they don't work well at all (like the sony erricson , which shows their default locker after unlocking with the installed locker) .
is such a thing possible? maybe there is a path to the apk (or whatever) that is responsible of showing the lock screen?
is it also possible to backup what is responsible for the lock screen?
The android lockscreen are not handled by apk's. They're part of the framework itself ( except for the FaceUnlock). What you could do is to add another IBinder interface to "com.android.internal.policy.impl.LockPatternKeyguardView.java". Have a look at how "FaceUnlock" is implemented.
Regards,
Robert