I believe you can add a plain javascript function to your send function (well, you'll have to create one first -- it looks like you are currently using the angular scope.send(...)
).
<md-button class="md-raised" ng-click="clicked(); sendMsg(msg)"
Then in your sendMsg function, make sure they really want to continue before sending:
function sendMsg(msg) {
if (confirm("Are you nuts?!?")) {
$scope.send(msg);
}
else {
console.warn("Whew! Crisis averted...");
}
}