可以这样做：

function ChckbxsCtrl($scope, $filter) {
    $scope.chkbxs = [{
        label: "Led Zeppelin",
        val: false
    }, {
        label: "Electric Light Orchestra",
        val: false
    }, {
        label: "Mark Almond",
        val: false
    }];

    $scope.$watch("chkbxs", function(n, o) {
        var trues = $filter("filter")(n, {
            val: true
        });
        $scope.flag = trues.length;
    }, true);
}

和模板：

<div ng-controller="ChckbxsCtrl">
    <div ng-repeat="chk in chkbxs">
        <input type="checkbox" ng-model="chk.val" />
        <label>{{chk.label}}</label>
    </div>
    <div ng-show="flag">I'm ON when band choosed</div>
</div>

工作： http://jsfiddle.net/cherniv/JBwmA/

更新：或者您可以方法，例如：

UPDATE: Or you can go little bit different way , without using $scope's $watch() method, like:

$scope.bandChoosed = function() {
    var trues = $filter("filter")($scope.chkbxs, {
        val: true
    });
    return trues.length;
}

在模板中do：

<div ng-show="bandChoosed()">I'm ON when band choosed</div>

小提琴： http://jsfiddle.net/uzs4sgnp/