title: Getting accelerometer data in background using CoreMotion
body: <p>I'm unable to receive accelerometer data in the background, despite the seemingly correct solution per this question <a href="https://stackoverflow.com/questions/8716466/how-nike-gps-on-iphone-receives-accelerometer-updates-in-the-background">How Nike+ GPS on iPhone receives accelerometer updates in the background?</a></p>
  
  <pre><code>[_motionManager startAccelerometerUpdatesToQueue:[[NSOperationQueue alloc] init]
                                           withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) {
                                               dispatch_async(dispatch_get_main_queue(), ^{
                                                   NSLog(@"perform");
                                                   [(id) self setAcceleration:accelerometerData.acceleration];
                                                   [self performSelectorOnMainThread:@selector(update) withObject:nil waitUntilDone:NO];
                                               });}];
  </code></pre>
  
  <p>perform is logged whenever the app is in the foreground, but whenever I exit out to background it stops running. Does anyone have any idea why this might be? I've checked "Location Updates" in Background Modes...</p>