desktop.jsx

/** @jsx React.DOM */
'use strict';

var React = require('react');
var DesktopApp = require('./desktopApp');

React.renderComponent(<DesktopApp />, document.body);

desktopApp.jsx

/** @jsx React.DOM */
'use strict';

var React = require('react');
var DesktopApp = React.createClass({

    getInitialState: function() {
        return { counter: 0 };
    },

    componentDidMount: function() {
        var self = this;
        window.setInterval(function() {
            self.setState({ counter: self.state.counter + 1 });
        }, 1000);
    },

    render: function() {
        return (
            <div>
                <h1>Hello desktop world!!</h1>
                <p>val: {this.state.counter}</p>
            </div>
        );
    }
});

module.exports = DesktopApp;

mobile.jsx

/** @jsx React.DOM */
'use strict';

var React = require('react');
var MobileApp = React.createClass({

    getInitialState: function() {
        return { counter: 0 };
    },

    componentDidMount: function() {
        var self = this;
        window.setInterval(function() {
            self.setState({ counter: self.state.counter + 1 });
        }, 1000);
    },

    render: function() {
        return (
            <div>
                <h1>Hello mobile world</h1>
                <p>val: {this.state.counter}</p>
            </div>
        );
    }
});

React.renderComponent(<MobileApp />, document.body);

package.json

{
    "name": "example_app",
    "version": "0.0.1",
    "devDependencies": {
        "react-hot-loader": "0.2.0",
        "jsx-loader": "0.11.0",
        "webpack": "1.3.2-beta5",
        "webpack-dev-server": "1.4.7"
    },
    "dependencies": {
        "react": "0.11.0"
    }
}

webpack.config.js

var webpack = require('webpack');
var path = require('path');

module.exports = {
    entry: {
        desktop: ['webpack/hot/dev-server', './desktop'],
        mobile: ['webpack/hot/dev-server', './mobile']
    },
    output: {
        path: path.join(__dirname, 'build'),
        publicPath: '/build/',
        filename: '[name].js',
    },
    resolveLoader: {
		modulesDirectories: ['node_modules']
	},
    resolve: {
       	extensions: ['', '.jsx', '.js']
    },
    module: {
        loaders: [
            { test: /\.jsx$/,  loaders: ['react-hot', 'jsx'] }
        ]
    }
}