In recent years, Sony has become a Good Guy Greg for developers and users by allowing them to unlock their bootloaders and by releasing kernel source code in a timely fashion. Many of their devices and Android modifications are quite unique. Some devices, like the Xperia Tablet Z have an interesting baked-in feature that uses screen to wake their devices by simply double tapping on the screen. The double tap to wake feature was originally exclusive to that tablet. But thanks to AOKP team, users can now use this feature on the Xperia Z family of smartphones.
XDA Senior Member championswimmer recently merged a kernel patch that adds double tap to wake support for the Xperia Z, ZR and ZL. His investigation showed that the necessary drivers were already available in the source code, but were locked. The developer added and removed a few lines in the source code, and now the apq8064 family has this feature available. Battery drain shouldn’t be a problem, as it’s a built-in function of the Synaptics ClearPad touch matrix, and it works pretty well on the aforementioned tablet.
To test this feature on your own device, you need to install the newest version of AOKP, which can be found in the development threads for Xperia Z, Xperia ZR, and Xperia ZL.