motion sensor to activate Pi touchscreen (or really any DPMS screen)

config.json

{
    "host" : "XXX",
    "port" : 1883,
    "username" : "XXX",
    "password" : "XXX",
    "presenceTopic" : "sensor/XXX/presence",
    "screenTopic" : "sensor/XXX/screen"
}

main.js

var gpio = require('rpi-gpio'),
    mqtt = require('mqtt'),
    config = require("./config.json");
    execSync = require('child_process').execSync;

var pin = 11;

var client = mqtt.connect(config);

client.on("connect", function () {
    gpio.setup(pin, gpio.DIR_IN, gpio.EDGE_BOTH, function() {
        var currentPinState = false;

        gpio.read(pin, function(err, value) {
            setPinState(value);
        });

        function updateTopic(topic, value) {
            client.publish(topic, value ? "ON" : "OFF");
        }

        function setPinState(value) {
            console.log('Value is now ' + value + ' @ ' + new Date());
            currentPinState = value;
            updateTopic(config.presenceTopic, currentPinState);
        }

        function turnOnMonitor() {
            execSync("sudo -u pi xset dpms force on -display :0.0");
        }

        gpio.on('change', function(channel, value) {
            if (channel == pin) {
                setPinState(value);
                turnOnMonitor();
            }
        });

        function checkDpms() {
            var monitorState = execSync("sudo -u pi xset q -display :0.0").indexOf("Monitor is On") > -1;
            updateTopic(config.screenTopic, monitorState);
            if (!monitorState && currentPinState) {
                console.log("Monitor is off, but pin is on; turning on.");
                turnOnMonitor();
            }
        }

        setInterval(checkDpms, 500);
    });
});