Ok,
Is there currently a way to integrate with Ignition?
Is there an open-source platform that provides an API or is it possible through custom scripting?
Probably. What have you tried? The 'turn key' solution is not available until 8.3. Anything you can find in the meantime is going to take some effort on your part.
You don't need Webdev for outgoing HTTP calls; you can use system.net.httpClient - you'll just have to figure out how to authenticate and make the appropriate requests to Whatsapp.