Handy could work in the UK except that it is extensively used already as an adjective eg: "that's a bit handy" or "you'll find this handy" etc. "That's a handy handy" would be a bit weird and as we already have mobile then there is no need for it. I suspect that "cell" will creep in eventually but not yet.
Etymology can be quite interesting 8)
Without any research whatsoever I'll also venture that "blowing" is what people used to do when they had to rush downstairs to answer the new fangled telephonic device and ended up out of breath. However, again without research, there is a good chance that the RN and co would have referred to the voice tubes on ships as "blowers" because that is the sort of word they would pick. I know a lot of modern matelots and that theory fits nicely.
Although blower is slang for a phone in the UK.