Traceability in Agile Projects

I've been thinking a lot over the last couple of years about what an entry-level requirements and/or modeling tool would look like---something that undergrad students would find so useful in courses that they'd actually want to use it (instead of just going through the motions to get a grade). Over at InfoQ, there's a good summary of some interesting discussion about traceability in agile projects that I think is relevant.