The House of the Dead: Overkill is making its way to iOS devices soon. "The Lost Reels" is a "remixed" version of the original Wii light gun shooter.
The initial $4.99 download includes two "movies," each with four levels and a boss fight: Papa's Palce of Pain and Ballistic Trauma. Additionally movies can be purchased for $1.99 via in-app purchase.
You'll also be able to buy in-game "Koins" with real-money, but Touch Arcade says that simply playing the game offers "more than enough" to upgrade your weapons. Although the weapon upgrades are permanent, you can also buy other temporary items that boost damage dealt or Koins earned.
Oddly, the iOS version of Overkill uses virtual analog controls. There's also an option for aiming using the accelerometer. A third option called "Frenzy Tap" may actually involve touching the screen, but apparently remains locked in the game. It makes sense that directly touching the screen to shoot zombies may make the game much too easy, but a virtual analog stick doesn't sound very pleasant to use for this genre of game.