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DebugView is an application to monitor debug output.

From Microsoft TechNet:

DebugView is an application that lets you monitor debug output on your local system, or any computer on the network that you can reach via TCP/IP. It is capable of displaying both kernel-mode and Win32 debug output, so you don’t need a debugger to catch the debug output your applications or device drivers generate, nor do you need to modify your applications or drivers to use non-standard debug output APIs.

Link

Here is a small example of how to create a low level keyboard hook with the Win32 API. Example can be found here.

Here is a link to a C# command line parser library: link