Hrm.. While I mostly blame Vodafone for this exploitable and weird offer, I question the idea of using this hack to advertise Fx for developers.

It's novel mostly because of the strange environment, not due to the couple of lines of code to implement the hack.

And finally, I have a hard time believing that you couldn't do something comparable with Tasker etc. - or with a tiny Android app of your own (but I haven't tried managing calls so far, I might be off).