The other day we saw Speed for Maps adding a speed meter to Google Maps and today it is Compass for Maps' turn.
Compass for Maps adds a compass to the Google Maps application in the lower right corner so that you never get lost in the city, although I personally prefer the built-in compass of the native application.
You need an iPhone 3GS or 4 for it to work.
You can download it free en Cydia.
You need to have done the jailbreak.