Do you need buttons to play games on your iPhone? Certainly not. And yet, iOS MFi-certified game controllers are here, giving you the promise of full game controller-like support and letting you theoretically use your phone or iPod Touch like a little Nintendo 3DS or PlayStation Vita.
The Logitech Powershell Controller + Battery is one of those accessories. As its name suggests, it's a case that adds physical gaming buttons, and also has a battery pack. It also costs AU$129.99. For most people, that's where the train skids off the tracks.
Whether you want an iOS game controller probably depends on two things: how many cool games there are that support it, and how much it costs. At the moment, that's the failing of all iOS game controllers: the accessories, like the Logitech PowerShell Controller + Battery, simply cost too much. And what they do just isn't interesting enough... yet.