title: Check if Sensor.TYPE_SIGNIFICANT_MOTION is hardware supported
body: <p>I'm going to use Activity Recognition API to do some optimizations on an App.
  In short I need to know when a device is STILL. But I do not want the App became battery draining by leaving sensors always on.</p>
  
  <p>On  is reported:</p>
  
  <blockquote>
    <p>To conserve battery, activity reporting may stop when the device is 'STILL' for an extended period of time. It will resume once the device moves again. This only happens on devices that support the Sensor.TYPE_SIGNIFICANT_MOTION hardware.</p>
  </blockquote>
  
  <p>I would register to ActivityRecognitionAPI only for devices that support significant motion detection by HW.
  But I cannot find a way to check when this support exists.</p>
  
  <p>Using:</p>
  
  <pre><code>    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
      Sensor sensor = sensorManager.getDefaultSensor(Sensor.TYPE_SIGNIFICANT_MOTION);
      boolean supportSignificantMotion = (sensor != null);
  </code></pre>
  
  <p>does not discriminate if support is by HW or by SW (on most devices this may be implemented just by software on accelerometer sensor).</p>
  
  <p>Does anyone know if is it possibile to perform that check?</p>
  
  <p>Thanks</p>