app.js

module.exports = function(server) {
  var buttonQuery = server.where({type: 'button'});

  server.observe([buttonQuery], function(button){

    button.on('click', function(b){
      //This will log undefined because there are no inputs to this transition
      //You can use dot notation to access properties on devices
      //console.log(b);
      console.log(button.b);
    })

  });
}

index.js

var Device = require('zetta').Device;
var util = require('util');

var Button = module.exports = function(n) {
  Device.call(this);
  this.name = n || 'Button';
};
util.inherits(Button, Device);

Button.prototype.init = function(config) {
  //Name is set in here.
  config
    .state('ready')
    .type('button')
    .name(this.name)
    .when('ready', { allow: ['click'] })
    .map('click', this.Click);
};

Button.prototype.Click = function(cb) {
  cb();
};

server.js

var zetta = require('zetta');
var Button = require('./devices/button');

var app = require('./apps/app.js');

zetta()
  .use(Button, 'Lights')
  .use(Button, 'Camera')
  .use(app)
  .listen(1337);