arduino.js

var arduino = require("johnny-five")
, board = new arduino.Board()
, SendGrid = require('sendgrid').SendGrid
, sg = new SendGrid("your_sendgrid_username", "your_sendgrid_password");

board.on("ready", function() {
  var button = new arduino.Button(8); // Button on pin 8

  button.on("up", function() {
    sg.send({
      to: "john.doe@example.com"
      from: "jane.doe@example.com",
      subject: "This email will be sent when you press the button",
      html: "Go check your inbox!"
    });
  });
});