To demonstrate how insecure and simple the WhatsApp protocol really is, I sat down and created this quite simple web-based client for WhatsApp. You can simply authenticate with your phone number and your WiFi Mac-Address (iPhone) or your IMEI (Android and others)
It's based on venomous0x's WhatsAPI PHP API which I ported to node.js.
Please note that you can only be logged in with one device at a time, so please turn off WhatsApp on your mobile device first. Also, you will not get the messages sent and received through this app on your phone.
We do not log any of the transmitted data.
The service is currently not available right now due to server-side changes done by WhatsApp Inc. To get notified as soon as it's back online, follow @rattazong on Twitter.