Gezzz I'd never though of one of those for new construction.
That ,would ,,,be a good safe/gun/reloading room or shelter wouldn't it now!!!! Use it as the inside form for the cement walls and make a door set in to it, going to the rest of the basement with a vault type door you can get easily and your golden. Great idea if you're in a typically dry area where cellar moisture isn't a problem.
What a good idea. Food for thought for folks in tornado prone areas and not that much more overall cost when doing a new construction , at least I wouldn't think it would cost to much more. Certainly cheaper than a stand alone unit though.