My first observation is that in most of the apps I've worked on keys are composed by constructs such as `t :"something_#{from_the_context}"`, which I assume this tool will miss. I'd much rather see a tool that tracked i18n hits in a k/v store, and used that in addition to the static analysis.

Don't let this discourage you, your work looks great (props on the correctly tabulated output!) - but it would never work for me in what I think is a reasonable usecase :(