拦截Android的操作系统来电屏幕并替换

I would like to intercept the Android's OS incoming call screen and replace it with my app's incoming call screen. However, there is no API to do so, but I know for sure it is possible as 4 different companies implemented this; The companies I'm talking about are: Adaffix (Yellix), Vringo, WhitePages Caller ID and more. They are all cleanly replaces the OS incoming call screen with their app's incoming call screen as the call arrives (no delay, no glitches, it is always working).I would like to intercept the Android's OS inco