Bangle.js Button Integration

Hello! My thesis group decided to use Bangle.js as our open-source smartwatch for our study. Our thesis title is 'Distress Call for Physical Assault Victims using Smartwatch and Mobile Application' which utilizes the heart rate sensor from the Bangle.js and sends the data obtained to the mobile application that we will will be developing. With 2 presses from the button of the Bangle.js 2 smartwatch, the heart rate sensor starts reading the heart rate of the wearer.

I'd like to ask the following questions:

1. If it is possible to modify the firmware to program the button from the Bangle.js
   
2. What modules do we need to use for the button and the heart rate sensor
   
3. What ways we can send the data from the heart rate reading to the mobile application (we have thought of using Bluetooth since it is a companion app)
   
   

I'm also open to suggestions and tips. Thank you so much! ^_^

1. You don't need to modify the firmware to use the button, there are several functions for that (setWatch or setUI)
   
2. No extra module, button see above, HRM http://www.espruino.com/Reference#l_Bangle_HRM
   
3. The bangles only way to communicate to other devices is with Bluetooth, so yes, use that.