You can use any headphones with a 3.5 mm jack. For the techies: that's TRRS (stereo-plus-mic) with OMTP and CTIA/AHJ.
A bit longer explanation:
First of all, Fairphone did not produce a headset for our device.
All regular music headsets with an 3.5mm audio-jack should work with the Fairphone 1 for media playing. An audio-jack is the end connection of the cable.
If you want to buy headsets with a controller on the cable it’s more difficult. There are many different headsets available in the market. Most headsets have a 3.5 mm audiojack; the difference lies mainly in the audiojack itself. The connection has a couple of rings (3 or 4) and the way the headset functions depends totally on this configuration. The manufacturers have preinstalled the hardware settings through these stripes.
To clarify: for our phone that is TRRS (stereo-plus-mic) with OMTP and CTIA/AHJ. We’ve tested a couple headsets (including mic and remote control function) of other brands. Both headsets contain a remote control panel in the cable with 3 buttons on it.