Neat but it looks like a pain in the butt to me. Got to keep the string dry or it's not going to work. Plus metal gets hot so I know for a fact that I'd burn my fingers on the tube, LOL. You'd also kind of have to wait for the tube to cool down before storing it away, perhaps.
I'd just as soon carry cotton balls with petroleum on the them or commercial tinder cubes. I have the cubes now, and they burn HOT and for several minutes. They'll also burn while floating on water. No moisture issues with them.