Keyboard shortcuts in iOS?

The only way (that I know of) to get input from the keyboard in iOS is using the UITextInput protocol. Unfortunately, the protocol doesn't give you the raw keys that were pressed, and instead sends you messages like "insert this string" and "move the caret to this position." So in order to know that an arrow key was pressed would require you to do some digging.

As for shortcuts with modifier keys, like copy/paste or undo/redo, Apple only seems to support the basics, and doesn't allow you to create custom ones. They use methods in UIResponder: –canPerformAction:withSender: and undoManager.

So if I were writing a game and wanted to take advantage of the keyboard I would subclass UIResponder and have it conform to the UITextInput protocol. And then make it the first responder. This however will probably bring up the software keyboard if a physical one is not present.

My own disclaimer: I haven't done all the hard work to use UITextInput in a way it wasn't meant to be used, so I don't know how feasible it would be to actually get it working. And I don't really want to. Rather, let's all file bug reports to get Apple to create an API that allows us to get more precise input from the keyboard.

In iOS 7, the UIResponder property keyCommands and the class UIKeyCommand were added to support shortcuts. Simply override keyCommands to return an array of UIKeyCommand and you should be good to go.

Worth mentioning: Though the details are currently under NDA, Apple is adding support for keyboard shortcuts/events in iOS 7.

I suspect it will work similarly to how it works on Mac OS X, which is briefly described in this answer to a similar question.