You can use following commands to check the memory/performance/memory-leaks of your applications during development.
- /usr/bin/top or top
- /usr/bin/vmmap or vmmap
- /usr/bin/leaks or leaks
If you have XCode and Apple developer tools installed (you get in CD), you can find more tools in /Developer/Applications/Performance Tools
It takes sometime to understand tools, but it’s really useful while development. One of the reasons, I started using Mac OSX because it’s on top of *nix and there are good free tools that comes with it (in CD/DVD).
You can get lots of Open-Source/FSF tools ported for Mac OSX (and Darwin) using Fink or Darwin Port package management tools.