Creating a Windows Game Overlay Application?

After playing quite a bit of Bad Company 2 over the last month, I'm getting kind of tired of Alt+Tabbing out of my game to change the song on iTunes. I've got a fairly good iTunes controller library already built for a previous project I was working on, and I'd like to create a WPF application mimicking the BC2 UI that would overlay the game when pressing a shortcut key, much the same way as 开发者_高级运维the Steam Community overlay.

The only problem I foresee is getting my application to overlay BC2 when the user presses a specified shortcut key in-game. Is there a way to intercept a keypress from BC2 (or, really, any Win32 application) and use it to bring my app to the foreground?

In order to have a global keyboard shortcut, you need to use a Hook.

Here is a tutorial showing how to do Keyboard Hooks in C#.

That being said, doing the overlay may be difficult, depending on how the game is written. Many full screen games cannot (easily) have other programs run in front of them. I'd play with making sure that works correctly in your specific game first.