The first one pops-up a little window that let you easily navigate your code structure components. In a way it is similar to the structure pane in JDeveloper - but you don't need to move your mouse out of the coding editor to get to it. Just Ctrl+Shift+T and you'll get it. Then use your keyboard to quickly type the letters of the object you are looking for - press enter and you are there.
The second extension brings you finer highlighting control to methods and member variables.
John Richardson - the guy who wrote both works in the EM group at Oracle. And is using JDeveloper to code - he was missing these two features - so he just wrote them.
And to go even further - you can get the code to both extensions and learn from it how to build your own little gadgets.
Just make sure to share it back with the JDeveloper community.