I haven't tested it yet but I like to be able to inject into running native apps and control them, debug them, etc. On MacOSX, there is the SIMBL project which

I haven't tested it yet but I like to be able to inject into running native apps and control them, debug them, etc. On MacOSX, there is the SIMBL project which enables such a plugin architecture for any OSX apps. E.g. you can get extra features like window-always-on-top, window-transparency, etc. And you can automate / script some apps which would not be scriptable otherwise or to such extend. Or you could add specific features to applications. E.g. Dropbox on MacOSX uses a technic like this to display some state-icon of its Dropbox directory in Finder. Some links to SIMBL: https://github.com/norio-nomura/EasySIMBL https://github.com/norio-nomura/EasySIMBL https://code.google.com/p/simbl/wiki/SIMBLPlugins https://code.google.com/p/simbl/wiki/SIMBLPlugins SIMBL would inject other native code into to some app. In most cases you would inject other ObjC code. I like the idea to dynamically script or mess around with an app. For that reason, I used SIMBL to inject Python + iTerm + PyObjC. That way, you can interactively interact with any app with Python. https://github.com/albertz/Pyjector https://github.com/albertz/Pyjector A similar project is this: https://github.com/albertz/FScriptAnywhereSIMBL https://github.com/albertz/FScriptAnywhereSIMBL And this Frida looks like a similar more modern project with JavaScript and support for Windows, Mac, Linux, iOS and Android.