You can download Grayd00r, an iOS 9-themed custom firmware and tool for iPod touch 3G and the original iPad 1 that offers a bunch of new features and improved performance. The Whited00r successor also has an Apple TV 2G variant that, for now, only brings the Apple TV 3's flat UI to the old set-top box.
You can now get iOS 9 Picture-in-Picture (PiP), Split View, Slide Over multitasking features on iPhone and unsupported iPad models. Here's how!