Have a Galaxy Note - had all the Dom Joly jokes when I got that. Is obviously so shite and unloved that they've released a second one and pretty much all top end phones now are about that size.
Have just bought the Asus, and am going thru the same - as previously put, it's really surprising that this hasn't been done in a more mainstream manner before.
For me, using a set of headphones with a microphone appears to work ( despite the handbook saying that the audio jack is one way only, so could just be a really good pickup on the inbuilt mic ).
Am tempted with the 'break the bluetooth' idea, build it into a stylus maybe.
Am I bothered about looking a twat on the train ? Nah, I work for a bank, so any early morning/late evening calls make me look like a twat any way.
Have fun, play nice.