Ordinary headphones with volume potentiometer. What if i need just next/prev song and stop/start playback commands? By sensing resistance of the load/output current on amplifier all can be acheived (by two buttons):

* either left or right resistance is high (no volume, small current) -- prev./next
* both are high -- stop if playing, play if stoped (or on/off chain + application decides)

IRDA, Bluetooth with loads of drivers and protocols, inflexible pointing/control by additional tools are not needed. Yet hardware sensor in PC sound cards, its driver, userspace ALSA/or other way of event notification aren't that simple.

Yes, and headphone manufacturers must be convinced to provide two additional buttins near volume control.