You can buy the USB Infrared Toy v2 from Dangerous Prototypes and get right to turning cheaply made IR devices off and on but you would miss out on a chance to build one yourself.  If you follow the links from Slashdot you will get a quick tutorial on how to determine the oscillation frequency of a broadcaster by looking at the components of the circuit and how to use an Arduino UNO to create your own.  If you are already familiar with this type of project consider teaching someone who needs their fear of electronic devices reduced through understanding how these magic boxes work.

"Cheap home alarms, door opening systems and wireless mains switches can be bypassed with low-cost and home-made devices that can replicate their infrared signals. Fixed-code radio frequency systems could be attacked using a $20 'toy', or using basic DIY componentry."

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