I'm curious if you're trying only with the screen off, or with it on as well.
For me, all of the buttons except for the power button work very inconsistently with the screen off: the volume buttons on the phone, the camera button, and the headset button. They work 100% of the time with the screen on. I think it's just a software bug when the screen is off.
Also, other than the above issue, I believe that any single-button iPhone compatible headset should work. That's been my experience with three different headsets, the Etymotic hf2, the Phonak PFE122, and the Meelec M6P. Three-button iPhone headsets will not work because they do something proprietary.