Wixel Wireless USB Module from Pololu is a great little general purpose wireless device that allows you to send data to/from remote nodes. It is well documented and easy to use. See the Wixel Arduino Shield if you want to use this with your Arduino.
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Wixel Wireless Arduino Shield. This Arduino shield accepts the handy Wixel wireless USB module, which allows you to wirelessly control and program your Arduino board.
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