How do i create an application that is usable DURING a PC game?

[roblong]

This is what im looking for: Ill be playing a PC game where my game window is maximized and desktop is not accessible from within the game, I would like to have the application running in the background, and by me pressing a preset hotkey, my application will now be visible IN GAME as well as being able to use my mouse and keyboard to edit text fields, and to click command buttons. Any and all help would be greatly appreciated.

[RhinoBull]

Why would you want that? Please explain.

[roblong]

Why would you want that? Please explain.

My application is going to be for team scrimmages, clan wars, battles, 1v1's and etc. I want users to be able to be playing their preferred game, and if they just happen to get called out by an opposing team during their gaming to have a scrimmage or clan war, they would simply pull up the application in game, register their team/opposing team, number of team members, things like that. Then once they fill out the form in the application, its going to be implemented into an HTML form i already have on my website as a test, then run through a PHP script to register them for a battle so that records can be kept.