Advanced Task Killer for Android phones

Is there an application in Android phones that will allow me to do multitasking and kill open applications? An iPhone has this feature and I would like to know if there is an Android application that will let me kill multiple open applications at once, just like with an iPhone. Is there an Advanced Task Killer for Android phones? And also, I do not want to keep on opening an application to see how many cells I have used and how many data I have inputted. I want to know if there is a data monitoring application that can run in the notification center.
