It seems to me that the 'unanswered questions' list is not always very helpful. The reason is that there is often a comment (or several) which fully solves the problem, or at least gives a large enough hint to render a full answer pointless. What would be more useful is a list of questions with no upvoted comments. Is this a feature that anyone else would agree with?
I think perhaps a better solution is for those people who have commented with an answer to answer the question, or perhaps have a moderator turn their comment into an answer. No need to reinvent the wheel.
(I was actually writing this answer as a comment, until I realized the irony...)
The fact that upvoted comments are often answers is, I think, basically peculiar to math.SE (in my experience). If you browse other SE sites you'll see that in many other places upvotes usually go to strong complaints or funny observations instead. So I don't think this would be useful across the network.