Xcode/iTunes/Instruments central toolbar item; what's it called and how do I create one?

Question

I'd like to create a toolbar item like the central item seen in Xcode/iTune/Instruments/etc:

Can anyone tell me what it's called and how to go about creating my own?

Also, will I face problems getting my app approved by Apple when I submit it to the Mac App Store, for imitating Apple's own apps too much?

Answer 1

I finally implemented the solution from here:

iTunes or Xcode style information box at top of window

Here are the initial results: