Edit: I spoiled it for myself by Googling, and of course that product already exists. Even Belkin have one: http://www.amazon.com/Belkin-Headphone-Adapter-Remote-shuffl.... There's also a DIY solution: http://www.depotbassam.com/2012/01/diy-smartphone-headphone-....
> You can still use it if you have a pair of headphones in too, with the cans' play button subbing in for control.
Sadly, my headphones do not have a button, and I wont be on the go without them, so sadly Pressy is not for me.
One of my long-term disappointments with Android is that they never used the modified plug the iPhone uses that also allows for volume control. But then, Apple may have patented it.
Not that all manufacturers seem to care since I have a handful of Nokias that do the same thing...