Had a thought this morning that wifi could be used to do some pretty rad stuff… like detecting when I get home by noticing my iPod touch.

Since most of us carry wifi-enabled devices with us at all times, and most of us have them set to auto-connect once in range of our routers, I thought, why not use that data?  It could be as simple as logging coming and going, or as sophisticated as automatically turning on my favorite music when I walk in the door.  Or even adjusting the thermostat when I arrive home to save energy when nobody is around.

As a very brief proof of concept I whipped out a simple algorithm in PHP which can be run from any Linux computer on your network.

Usage:  php wifi-check.php –device=devicename

 0) {
      $tmp=@explode('=', $ping);
      $result=@explode('/', trim($tmp[1]));
    }
    if (count($result) > 0) {
      // Now we know the device is connected; do something
      echo 'Device active.' . PHP_EOL;
    } else {
      // Device is not connected.
      echo 'Device inactive.' . PHP_EOL;
    }
  } else {
    echo 'Usage: php wifi-check.php --device=devicename' . PHP_EOL;
  }
} else {
  echo 'This script is designed to be run from the Linux terminal, not a browser.';
}
?>

My thinking is to put something like this in a looping script and let it run every so many seconds or something, calling particular functions if the device is detected as active vs inactive.

I’d welcome your thoughts in the comment section below.  What practical things could this be used for?