Injecting Keyboard\Mouse\Touch events - Windows Application vs. Windows Service

I'm trying to implement a C++ Windows 8 application that receives an input from the user (from external device\file\etc..) and simulates keyboard\mouse\touch events. I want the application to run in background and in log-on screen (to simulate Ctrl+Alt+Delete keyboard event for example).

I've been trying to use Windows Service (as it runs in background and in log-on screen as far as I understood), but injecting keyboard events doesn't work. The suggestion of checking-on "Allow service to interact with desktop" in SCM didn't work as well.

My questions are:

1. Is there anyway to inject keyboard\mouse\touch events in Windows Service? (note: Windows 8, C++ Windows Service)
2. Is there any other type of Windows application that runs on log-on screen except for Windows Service?
3. In terms of Arch\Design, what's the best way to implement such an application taking into account that the log-on screen accessibility is optional?

Thanks in advance,

Hani;