The SonyEricsson Xperia X1-earphones (including the detachable microphone and button use the same standard 3.5mm-4-ring connector and work with the N900. I'm currently using the X1's wired microphone/button and Bose's Quiet Comfort 15 on top of them. Yes, lots of wires and major price tag, but REALLY great audio quality and you can still make calls without switching gear. Had no problems with this combo so far. The N900 even recognizes the X1's microphone as "Headset", not just as "Earphones" !