Re: Headphone volume warning...
The headphone volume nag is an EU requirement, I'm afraid, and is now built-in to Android.
You have to warn the user when the electrical output level goes above a certain amount and it requires a positive confirmation to go further. The music player (for it affects all such devices) must repeat the nagging for every 24 hours of music listened to.
Now, this obviously takes no account of how efficiently your headphones convert 'leccy into noise, nor if they are powered 'phones. God knows it took us an age to argue that it was irrelevant for BT devices... but PLEASE, won't somebody think of the children? ;-)