Make call from android phone when user click Puck.js button

There are a whole lot of threads on this kind of thing already. Either:

• Set Puck.js up to advertise the state of the button - subscribe to BLE advertising events with nativescript and then call the number then.
  
• Set Puck.js up as a BLE HID device - you can then just set a listener up for a specific keypress
  
• Keep a connection to Puck.js open and set yourself up to be notified if a characteristic changes - that's the way you'd do it with normal BLE devices, but it's a bit more trouble