Running along the left side, you'll find a power toggle, a programmable jog dial (preset as a microphone monitorvolume) and another for setting the volume of external sources like MP3 players.
Last year, Dutch chip-maker NXP released a new type of mobile audio component -- the TFA9887 -- that allowed a mobile device to monitor its speaker system in real-time in order to max out volume without risking damage to the driver.