There have been ROM after ROMs of the ever popular “pie” functionality added to Android devices, and now it looks like the feature will be “baked” into CyanogenMod nightlies.
This feature hides the Back, Home, and Apps keys (among others), and with a quick swipe of your finger, a half pie appears with these buttons. My explanation does not do it justice, so I suggest you check out the attached screenshot instead to understand what I am babbling about.
From CyanogenMod’s Google+ page:
Inspired by the much loved +Paranoid Android feature, itself inspired by the AOSP Quick Controls found in the stock browser, Pie Controls have landed in CyanogenMod 10.1 nightlies thanks to the efforts of contributor Jens Doll.
Jens took the time to completely rewrite the code and has been working with our UI and UX team to get all the groundwork in for this much requested feature. 
The two patches that enable this functionality were merged in late on the 25th of March, so expect them to be incorporated into the next set of nightlies that follow. 
As an added enhancement, Jens has also incorporated some additional ‘Pie’ functionality into the Phone UI. 
The code will allow for further expansion and enhancements, so expect more goodness to follow. For the time being, this should make for an excellent addition for all you Expanded Desktop users.
source | cyanogenmod google+