Razer's Junglecat is not the first iPhone game controller to hit the market, but its design may be the most pocket-friendly.
The Junglecat clips onto the iPhone like a protective case, and a panel of physical buttons slides out from the bottom. It's somewhat reminiscent of Sony's old Xperia Play smartphone, except that the controls aren't permanently attached to the phone.
The case should be fairly easy to fit into a pants pocket, though it does add a fair amount of bulk at 0.7-inches thick, 2.5-inches wide and 5.9-inches tall. An iPhone 5S by itself is about an inch shorter, 0.2 inches narrower and about 0.4 inches thinner.
Also, keep in mind that the Junglecat only has a directional pad, four face buttons, two shoulder buttons, and a start button. It's missing the dual analog sticks and rear triggers found on some other iOS game controllers, such as Moga's Ace Power and SteelSeries' Stratus, so it won't be much help for 3D shooters and action games.
On the plus side, Razer is promising some helpful software through the Junglecat companion app. This will allow players to customize the controller's pressure sensitivity and button mapping, and will also include a list of controller-friendly games--something that's sorely lacking in the App Store itself. Razer also says it will support Controller Forwarding, an iOS 8 feature that lets these controllers remotely connect to an iPad or Mac.
Like most other iOS game controllers, the Razer Junglecat isn't cheap. It'll cost $100 when it ships in July. We've seen prices on other controllers come down after launch, so it may be best to wait this one out.