Recent releases of Xcode supports a new debug symbol format called DWARF. One especially useful feature, is the ability to generate a symbol file that is separated from the application proper. This allows you to ship a stripped version of your application but still being able to decode the backtrace by using that symbol file (it is called a dSYM file).
The problem is that the current toolsets doesn't make it very easy to do this (essentially, only gdb supports DWARF/dSYM at this point). dSymbolizer makes it easy. dSymbolizer automatically starts the appropriate gdb executable depending on the architecture (ppc or i386) that generated the backtrace.