Bluetooth is very common wireless system available on most laptops and phones. Adding a Bluetooth modem to a microcontroller means you can then connected it via a serial stream to most phones or laptops and pass data in both directions. Suitable for computer-to-microcontroller communications. For serial communications between two or more microcontrollers consider XBee or Wixels.
Class 1 modules have higher transmission power and have a nominal range of 100m although in practicality ideal conditions of temperature, humidity, clear air and no interference are rare so a shorter range should be anticipated.
Class 2 modules have low transmission power so are limited to a range of 10m (30ft) or less with obstacles.
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