i,m using this iPad app to achieve this: air display
You have to install the program in your computer and your iPad.You can select duplicate windows o extended screen.The touchscreen area on the ipad works like if you are the mouse.
The only thing i can say it,s that works.But i really never did heavy use, only watch the tv on bed

. Now i will use more intense with this update and see how it works. I,m on mac.But it,s a pay app maybe someone knows a free app on the app store to share.
The bad thing: you can not use this with touchable or any other app, so you sacrifice a lot