I found this plugin SpecKing that looks like it's just about exactly what I'm looking for, I haven't tried it out yet though because I was hoping to find a free, maybe even open source alternative..
Does anyone know of any open-source and/or free Photoshop plugins similar to this one?
I'm looking to extend the functionality of the measure tool so as to actually display annotated measurements of the measured distances for convenient reference.. like a blueprint basically.