Sample of using Parse with the SendGrid Cloud Module. This example will send an email when other users comment on a picture in Anypic (https://parse.com/anypic).

parse+sendgrid.js

// Require the SendGrid Cloud Module
var sendgrid = require("sendgrid");
sendgrid.initialize("you@parse.com", "your_password");

// Run this Cloud Function every time a new Activity (such as a comment)
// is saved
Parse.Cloud.afterSave("Activity", function(request, response) {
  // Check if the activity type is a comment
  var activity = request.object;
  if (activity.get("type") === "comment") {

    // Get the owner of the photo commented on
    var targetUser = activity.get("toUser");
    targetUser.fetch({
      success: function(targetUser) {

        // Send an email if we have the user's email
        if (targetUser.get("email") && targetUser.get("email").length > 0) {
          sendgrid.sendEmail({
            to: targetUser.get("email"),
            from: "anypic@parse.com",
            subject: request.user.get("displayName") + " commented on your picture!",
            text: "Check it out at anypic.org!"
          }, {
            success: function() {},
            error: function() {}
          });
        }
      },
      error: function() {}
    });
  }
});