Pupil looks like a nice app to switch between multiple resolutions on a Retina MacBook Pro. The core feature of the app is a configurable menubar item that can list the resolutions you use the most, letting you instantly switch between them.

I can’t try Pupil because I don’t have a Retina MacBook Pro. However, Roman Loyola’s review at Macworld is positive. Pupil is $5 and there’s a free trial available.

I also like how you can “test” Pupil’s menu on the website.