iOS and Infrared

Is it possible to communicate with an Infrared device (USB Infrared, TV, Mobile Phone, etc) using iOS (iPhone or iPad)?

Well, i know it's possible, since there are many remote/universal remote applications in the AppStore. I basically want to know how?

What are the limitations and requirements?
What kind of additional hardware is required? If it's available in the market?
Which protocols should i know about?
Which iOS libraries can help me in the process.

Can anyone point me in the right direction. Thanks.

Solution

Any devices using IR for controllers are either wifi or have custom hardware that outputs IR signals based off of output from the device. So without using your own hardware, I don't believe this is possible