Mi Band 1 - No. Sadly it is not technically possible to implement any function when you tap the bracelet. The Mi Band hadware and firmware does not support broadcasting of the tapping event back to the phone. This means that the mobile device (phone / tablet) can never be notified about the tapping and can not stop or perform any action.
Many people would argue that when you're pairing the bracelet, you have to tap it, so it has to register the tapping somehow - yes, that is correct, but you must realize that during this, there is no signal back to the mobile device. What happens here is that the phone invokes pairing with the bracelet - the address of the mobile device bluetooth is sent to the bracelet. And all what the bracelet is waiting for is an approval - you approve the pairing on the bracelet by tapping it. When you tap it, the bracelet itself stores the hardware address of the mobile device within its memory. And it only sends and "acknowledge" of the pairing process. There is no notification event that would say to your phone "hey, I have just been tapped".
There is one vibration pattern, though, that is supported directly by the bracelet and that can be dismissed by tapping the bracelet. It is what Mi Fit uses for incoming calls and you can simply use it also with Mi Band Tools. To achieve this, set vibration pattern to Count = 1, Length = 10000ms, no repeating. This single long vibration pattern can always be stopped by tapping the bracelet.
In case the bracelet firmware would support broadcasting of the tapping event back to the phone in the future, I will I will surely implement it for some actions, e.g. to control music playback. But sadly the hardware and firmware does not support it currently.
Mi Band 2 - this is (partially) possible and already implemented in Mi Band Tools since version 2.4.0 in semi-active mode - what this means is that our implementation in Mi Band Tools offers you a dismiss ongoing notification pattern by tapping the bracelet or dismiss / snooze ongoing alarm by tapping the button or even automatically mute the incoming call together with stopping the bracelet vibrations by pressing the button. We've implemented this feature in the most battery efficient manner since we're not listening 24/7 for the button action but only at the time frame when we're also sending vibration signals into the bracelet. Thanks to this, our implementation of this feature has literally zero impact on the battery of your bracelet and mobile phone (unlike other "competitive" applications you can find on the Play Store). Read below to learn more.
It's important to note that this feature can never be implemented battery efficiently and stably enough to be used at all time. The thing is that without an hardware "passive" notification support, the mobile phone can not be passively notified about the button press event. What this means is that this feature can be only implementable in "active" mode - and if you would want to listen to the button for any action (e.g. to control music), your mobile phone would have to ask the bracelet every ~2-3 seconds whether the button was pressed or not.
What this basically means that your mobile phone would never be able to go into the sleep state. Your mobile phone would have to be waken up every few seconds, which would drain the phone battery extremely quickly (literally in few hours). Since number one priority for Mi Band Tools is stability and battery efficiency and we don't want to drain your phone battery in half a day (like the "competitive" button control applications on the store does), we're not planning to implement music control or anything similar that we don't find useful - we are focused on features that are reasonable and can be implemented effectively - that's why we do offer you battery efficient dismiss and snooze features by tapping the button since version 2.4.0.