do you mean the double knock the screen to awake the device?
if yes, i try last time, it is useless, when i am just standby within a min the k900, double knock, it will awake, more than that, it won't work,

In the end, i buy the original smart flip cover, everytime, i close cover, it auto standby, open cover, auto awake the system.

Due to the high sensitive touch screen, the first 3rd party cover I used, it will keep call to unknown ppl, when i close the cover with the screen remain at dialer. after switch to original cover, problem solve.