Originally Posted by Xyg:
The Pre comes with headphones with an inline microphone included in the packaging.
The Pre has a standard 3.5mm headphone jack.
Presumably, it's a 4-conductor jack to support the microphone as well, which means that iPhone headsets should work as well. When a 3-conductor plug (aka standard stereo headphones) is put in, the microphone input is just ignored.
Though, we don't know what (if any) advanced functionality will be present from a button, though I'd bet at least answering a call and probably redialing the last number will be supported.