Paranoid Android has been developing some rather interesting features but, unfortunately, they're initially only available for users of the custom ROM. Thanks to the power of open source and the efforts of computer science student Zhe Lu, Peek Notifications, one such interesting feature, is now available for almost anyone running Android 4.4.
In a nutshell, Paranoid Android's Peek Notifications is like a rethinking and improvement of the Moto X's Active Display notifications. It allows users to quickly take a peek at notifications even when their smartphones are locked. Peek uses either the gyroscope or the proximity sensor to determine if the user has actually picked up the device to start viewing the notification, otherwise it just keeps the display off.
Zhe Lu took the source code for Peek and tried to make it work for Android 4.4 devices, particularly his Nexus 5. He has made the app use public APIs so that it can work even without root and on stock OEM ROMs. He also did a bit of tweaking to make the UI easier to use. The result is a generic APK that can be installed on any device. However, there is no guarantee that it will actually work. There have been mixed reports even on the same device running the same Android version, so success is a bit random.
If you're willing to take it for a spin, hit the link below to look for the latest APK available. It's quite safe to try out, though you will need to give the app administrator access to lock the screen and view notifications. Do remember to disable those permissions first before trying to uninstall it, otherwise it will fail to be removed.