Do you develop apps with Appcelerator Titanium? It’s a great tool to create apps for iPhone and Android, but the lack of a debugger makes it difficult to find errors at runtime. You can use Titaniums logging function, but you have to remove all of them after you found your bug, because otherwise the flood of logging messages will drive you crazy. Trace for Titanium shows error messages and call stack only when an error occurs. And you can even use it to find bugs, when your app is out in the market.