client.html

<template name="example">
	<button id="button">{{buttonName}}</button>
</template>

client.js

Template.example.helpers({
	buttonName: function() {
		return "Button";
	}
});

Template.example.events({
	'click #button': function(event, template) {
		Meteor.call('exampleMethod', data, function(error, response) {
			// do something with response
		});
	}
});

Template.example.onCreated(function () {
	var ready = new ReactiveVar(false);
	// load reactive vars in here
	//
	// reactive vars used in helper functions or Template.autorun
	// functions get automatically reloaded on reactive var changes
});

Template.example.onRendered(function() {
	// load external js in here probably
});

package.js

Package.describe({
	name: 'example-package',
	version: '0.0.1',
	summary: 'example',
	git: ''
});

Package.onUse(function(api) {
	api.versionsFrom('1.0');

	api.use([
		'rocketchat:lib@0.0.1',
	]);

	api.use([
		'templating'
	], 'client');

	Npm.depends({
		'opentok': '2.3.0'
	});

	api.addFiles([
		'server.js'
	], 'server');

	api.addFiles([
		'client.html',
		'client.js',
		'tabBar.js'
	], 'client');

});

server.js

var OpenTok = Npm.require('opentok'),
	apiKey = "key",
	apiSecret = "secret",
	openTok = new OpenTok(apiKey, apiSecret);

Meteor.methods({
	exampleMethod: function(data) {
		syncMethod = Meteor.wrapAsync(openTok.method);
		response = syncMethod(method);
		return response;
	}
})

tabBar.js

Meteor.startup(function() {
	var settings = {
		i18nTitle: "Example",
		icon: "icon-example",
		id: "example",
		template: "example",
		order: 10,
	};
	return RocketChat.callbacks.add('enter-room', function() {
		return RocketChat.TabBar.addButton(
			settings,
			RocketChat.callbacks.priority.MEDIUM,
			'enter-room-tabbar-example'
		);
	});
});