PowerA has been one of the first to create controllers that can work with Android devices and Android games. The idea is simple in theory. You buy an Android phone, and then you hook up this controller to it, and play the more advanced games the way they were meant to be played - with a controller - and not with the fake virtual controller on the screen, which can make some games pretty difficult to play and enjoy.
The first Moga was not perfect, and not every game works with it, but the company has been improving the product, and now it's coming out with a Moga Pro controller, that should be available this spring. This version improves the grip of the smartphone, to make it more steady while you're playing, and it supports devices up to 3.2" wide.
But this has been my problem with Moga and other such controllers from day one. It would be very easy from an engineering point of view to make the grip contract and expand, even if you had to use some screws to put the device in place. But you'd only have to do it once for your device anyway. The advantage is that you wouldn't need to buy a new Moga controller every time you buy a new phone with a different size, and you could also use it on 7" tablets. I don't know whether they are not doing this because they haven't thought about it yet, or simply because they actually want you to buy a new one when you buy a new device.
This Moga set-up also reminds us about Nvidia's just announced project Shield. Some are asking why would you buy an Nvidia Shield, when you can just buy one controller like the Moga Pro, and pair it up with your device? And it's a very fair question. I think people who want that kind of flexibility and like to tinker like that with their devices, they'll definitely choose this option and use a Tegra 4 device, or something even better, and then have sort of a DYI Shield.
However, there are a lot of people out there who want something that "just works". They want the total package, and they don't want to "think" about all sorts of pairing issues and whatnot. Plus, Shield offers some other advantages like Steam PC streaming. So I don't really think that Moga and Shield and competing that much with each other, even though they look pretty similar in how they function.
On the other hand, everything is moving more and more towards smartphones, and the idea of a separate "portable console" makes less and less sense, but it's probably going to be a while longer until it fades away.