Memory leak detection tools
There is one specifically called Leaks and like a previous poster said, the easiest way to run it is straight from Xcode:
run -> Start with Performance Tool -> Leaks
It seems very good at detecting memory leaks, and was easy for a Non-C Head like me to figure out.
Select Profile from the Product menu in Xcode 6 to launch Apple's Instruments tool. (The application is located inside the Xcode application's package contents: /Applications/Xcode.app/Contents/Applications/)
A commercial alternative is OmniObjectMeter. (Discontinued by The Omni Group)