It's under a free license, lets you write hooks not only from C/C++, but also from any .NET language (architecture-independent). It makes any sort of API hooking a breeze.
Edit: Forgot to mention, it automatically sets up a remoting channel for you. That way, you can do IPC between your hooking application and the hookee trivially.
Comments
On the subject of Detours, I suggest checking out EasyHook: http://www.codeplex.com/easyhook
It's under a free license, lets you write hooks not only from C/C++, but also from any .NET language (architecture-independent). It makes any sort of API hooking a breeze.
Edit: Forgot to mention, it automatically sets up a remoting channel for you. That way, you can do IPC between your hooking application and the hookee trivially.