Once iPhone and iPod Touch only, Apple has updated the standalone Apple TV remote app, and for the first time has a specific iPad interface.
The app is mostly unchanged -- it still allows an iOS device to act as a remote control for the fourth generation Apple TV. However, official support for the iPad has been added, with a split-screen of sorts showing a window with cover art, with the left hand side of the screen mimicking the Siri Remote.
Text is easier to enter on the iPad than on-screen with the Siri Remote, given the pop-up keyboard on the iPad and iPhone.
Also added for both the iPad and iPhone is an enhanced Now Playing feature, with lyrics and playlists for music and chapters, and caption selection for videos.
The Apple TV Remote app is free, and occupies 12.6MB of device storage space.