Not aware of a servce that tracks mentions like this. The simplest method is to follow your competitor's account and review their posts on a regular basis. Track the volume of likes and comments on posts to learn what content is most effective. Content ranks higher than hastags (only in my experience and opinion). We operate the largest Instagram Services site on the net. PR1 and Position1 in our keywords.
Nice web site Michael S btw. We feature "ink" pages on our site.