I want to do a demo just like WaveSecure, which win Android Develop Challenge 2 with a third place. Now I have a problem in locking the screen customly, so I want to know how WaveSecure achieve its locking function, as the following picture show:

When the mobile is locked, WaveSecure can require customer to input their own password. So I think WaveSecure must replace Android's original locking function.
And I also google it, but I didn't find anything helpful. I only find two packages may be helpful. They are:
- android.app.KeyguardManager
 - android.os.PowerManager
 
But after I reading the Android Docs, I still can't have an idea on it.
Can you help me? Thx:)