Try Shady, Vaulty or SPC. I use SPC and it's pretty cool. I still can't figure out how to get the standard notification not to show, but the hiding of messages/phone calls is great. Shady is cool because it doesn't show up as an app -- you just dial "1, 2, 3" on your dial pad and it opens the app!
There's also another app called Hide it Pro. it shows up as "audio manager" in your launcher and allows you to hide images and/or video clips.
I didn't create any of these, but i read thru this thread and couldn't believe no one has mentioned these apps yet.