Mi Band 1S vibration on incoming call handling on iOS
<p>SO. Initial data:</p>

<ul>
<li>Device Xiaomi Mi Band 1 or 1S</li>
<li>Device paired with iPhone</li>
<li>Xiaomi iOS app has option "Vibrate on incoming calls"</li>
</ul>

<p>How they implement it? It continue works if you reboot device or force quit an app. It is unusual for default BLE background. Any ideas how this app handle events?</p>

<hr>

<p>For people who vote for closing this question. This is a very interesting issue which require some specific knowledge about bluetooth and background. For example there are three bluetooth background modes: <code>external-accessory</code> for old-school non-ble blueooth, <code>bluetooth-central</code> and <code>bluetooth-peripheral</code>. I have done a lot of experiments about last two. But it does not work as you expected after documentation reading. I have found few questions about this topic here on SO. All of them report about <em>pure predictable for bluetooth background</em>. And after all hours on this issue you see on Mi Band and them official absolutely legal app in App Store. And <em>this App keeps connection or has some other "magic" mechanism to handle calls and initiate reaction on device</em>. At a minimum it is curious. Is it? At a minimum it is useful for developers who works with peripheral devices.</p>