The Apple-jack :) is actually a TRRS (Tip-ring-ring-sleeve) 1/8th inch plug.
There are numerous adapters that will split out the two functions, here for example.
Apple has been known, however, to wire up their 1/8th inch jacks non-standard, making 3rd party adapters not work correctly. Not sure if your headset in particular falls into this category, but just be aware.
From the Wikipedia article on TRS:
Several mobile phones, particularly smartphones, feature 3.5 mm TRRS
connectors to facilitate attaching headphones/hands-free kits. 2
different forms are frequently found, both of which place left audio
on the tip and right audio on the first ring (mirroring the
configuration found on stereo connectors). Where they differ is in the
placement of the microphone and return contacts. The first, which
places the return signal on the second ring and the microphone on the
sleeve, is used by Apple's iPhone line, Samsung's Galaxy Nexus and
Nokia phones, among others. The second, which reverses these contacts,
is used by other Samsung smartphones and some Sony/Sony Ericsson