This is an interesting development indeed. I can see a mechanical pump extending the buttons when a cover is opened, which would not consume any power at all. That might be the best way to make it work. But it seems that the whole system life would be much shorter, meaning the phones may not last the complete six months to their intended obsolescence, which would mean that the makers would need to shorten the warranty time a bit. And anybody who is such an impatient jerk that they can't wait a few seconds for the buttons to extend should be sent back to using a rotary dial phone.