Last year we told you about GravityBox, easily one of the most complete and far-reaching Xposed modules for rooted Nexus and AOSP ROMs. The creator is still expanding the module, and has quickly incorporated the Heads Up notifications recently featured in CyanogenMod nightly builds. Heads Up notifications pop up for easy viewing and action while in full screen mode. The feature is hidden deep in Android 4.4 code, and easily enabled here.
The GravityBox implementation allows for deciding which notifications will appear as Heads Up windows and which will be ignored, and users can expand notifications (if supported) with a two-finger swipe. Other nifty additions to the tool set include better options for the "quiet hours" function, an expanded battery tile in the quick settings menu, user-definable actions for plugging in or unplugging headphones, and a lot of bug fixes and language translations. Check out the update post for a full list.
In order to run GravityBox, you'll need a rooted Android device running 4.1 or higher, and preferably a Nexus/Google Play Edition one, since it's designed for AOSP hardware and ROMs. Then you'll need to install and configure the popular Xposed Framework. Finally, grab GravityBox from its home on the original XDA thread. As always when tinkering with root-enabled software, it's probably a good idea to make a backup before you go digging into the various settings.
Thanks, Eduardo Ribeiro!