var app = angular.module('app',[]);

​

  app.controller('ctrl', function($scope) {

    $scope.buttons = [

      { name: 'cancelled', checked: false},

      { name: 'booked', checked: false},

      { name: 'something', checked: false}

    ];

​

    $scope.$watch('buttons',function(newVal,oldVal){

      oldVal = oldVal.reduce(function(p,k){ p[k.name] = k.checked; return p;},{});

      var changed = newVal.filter(function(k){ 

        return oldVal[k.name] !== k.checked;

      });

      changed = changed.reduce(function(p,k){ p[k.name] = k.checked; return p;},{});

​

     $scope.changed = changed;

​

    },true);

  });