Introducing Roundr
Roundr is an application that rounds the corners of your screen!

Functionality
Roundr features full settings which allow for adjusting the radius of the corners, as well as specifying which corners to enable or disable. With Roundr Extensions, you can customize the looks of the corners, and try out different designs!

Extensions
Roundr Extensions add 10 new corner styles, blacklisting apps (to hide rounded corners on certain apps), and more! https://play.google.com/store/apps/details?id=mohammad.adib.roundr.extensions

Development
Follow the development on XDA: http://forum.xda-developers.com/showthread.php?t=2234079