How to make a call when iphone shakes with particular threshold?

I am making an app in which i need to implement calling emergency medical services when mobile shakes with a particular threshold. Is it possible to capture the threshold or the extent of phone shakes and making a call when it happens? One requirement is can this is possible wh开发者_如何学Goen my app is not running?

I believe that the iPhone does not allow applications to run in the background. So the answer to your second questions is: No, this is not possible when your app is not running.