I've seen various voice services offer the ability to embed a "Call Me" button on their web page or an email. Some popular services with this ability include Skype and Google Voice. This would be an interesting feature. Consider a scenario when emailing a family or business contact. In the email you can offer them an opportunity to contact you on your OBi phone.
I suspect Firefox and the other major browsers will all support webRTC within the coming year making this feature all the more relevant.
Some early musings on this topic:
Call OBi button (WebRTC)
https://www.obitalk.com/forum/index.php?topic=6114.msg38965#msg38965
That would be cool. I use Google voice widgets. I would of course want the person to be able to put a name in that would show up on my caller id or allow me to identify that the call came from a widget.