This is a pretty old project now as it has been released about 2 years ago but seeing as no one has mentioned it here, I thought I'd share it to those of you who never heard of it.
I extended the /system/bin/app_process executable to load a JAR file on startup. The classes of this file will sit in every process (including the one for system services) and can act with their powers. And even more: I have implemented something that allows developers to replace any method in any class (may it be in the framework, systemui or a custom app). This makes Xposed very powerful. You can change parameters for the method call, modify the return value or skip the call to the method completely - it's all up to you! Also replacing or adding resources is easy.
If you, like me, enjoy customizing your rom to your own taste, say goodbye to the old irritating decompiling, compiling and pushing methods as with this framework you can modify your system by ticking and unticking boxes.
Another great thing is that this framework actually has an online repository @
http://repo.xposed.info in which you can download all sorts of modules that give you all sorts of modification abilities.
A few examples are
Wanam Xposed which I often use to customize my TouchWiz rom and
XBlast Tools for more general roms.
You can get the latest Xposed installer @
http://dl.xposed.info/latest.apkSimply download the apk file and install it. Run it from the app drawer, go to Framework and choose Install/Update.
