The multitasking tweak you guys are thinking of is called Quasar. Unfortuantly it's not updated for iOS 7. Matter of fact, I don't think it was ever updated for iOS 6. I wouldn't hold my breath for this. This tweak allowed you to multitask apps. It was pretty cool actually. There was really high demand for an iOS 6 update but it never came. 🙁
For just multitasking videos and some other app, like someone already suggested, you can use VideoPane by Ryan Petrich.