F-Script Anywhere lets you embed a FScript interpreter in any Cocoa application. You can use F-Script like a debugger, so you can examine your application's objects in a richer environment than GDB or Xcode permits. F-Script Anywhere can also be useful for examining applications you didn't write, to isolate bugs or add new features.
An alternative to F-Script Anywhere is PyInjector. PyInjector displays a list of running applications and dynamically inject both FScript and a Python interpreter into the selected application(s). PyInjector is available at http://end.com/speth/wp-content/pyinjector.html
F-Script Anywhere is part of the FScript distribution now.