I tried using a Motorola headset, bought from pasar malam. You need to cut the wire somewhere between the button and the earpiece before it would work. But somehow, the response is a bit weird, and I need to press a few times before it works.
Tried using a Nokia headset too. The moment I plug it in, it started taking photos automatically, photo after photo, like there's no tomorrow! Then I cut off the wire, but it no longer works...