Attached Link: http://www.netherworks-studios.com/

In the case of hair since it's parented to the head it stays on the head and moves with the head but won't come off if a pose is not saved correctly. But the lock function is also useful for many other cases, say for example you have your character posed and want to change the torso, arms, etc but not affect the rest of the body. You just lock certain parts and apply a pose that changes what you want. I have a set of body lock poses that locks various parts which makes it very quick to work with posing. I remember getting it from Netherworks though I'm not sure if it's still there, can't check because the scripts he's using are being blocked by my settings but see if you can find it. It's called Body Lock.