I got excited when I read their intro that talked about how mobile platforms lacked the real estate for proper debugging, until I realized there's no way this is going to help in current iOS mobile app development.

I'd be surprised to see Apple adopt this. It would be interesting to see this supported in the iPhone simulator at the very least.

It's not quite the same, but http://jsconsole.com/ is useful for providing a console for mobile devices.

This is what the "Debug Console" setting should be in the Safari->Developer menu.

iOS 5, maybe?