There needs to be a "universal volume control" app. One that gives you access to ALL of the volume controls available. Context-sensitive controls are nice: when I use the headphone jack for my car, the volume jumps up to its previously set level.
What would be better is to allow profiles. So "car" would set the headphone jack, AND "ringer (headphone)" to a certain level. But a "headphone" profile would let me set something different.
This would also allow for a "silence" profile, as the hardware switch for the ringer doesn't seem to silence the games/music.
This was to be my awesome app idea, but I don't have a Mac yet. But the need is greater than the length of time it will take me to get a Mac and learn iPhone development - so maybe someone else can write it? 😛