Adam, had you considered a strategic partnership with Wordtracker? Not only could you increase features and functionality but you would expose your brand to their customer base. Wordtracker has been around a long time and is considered a trusted source to most SEO old timers like myself, It would be the perfect marriage in my opinion.
The techies could manage the back-end integration and co-branding and perhaps on both ends users of each service could sample the other's technology then you could up-sell them on the full product which would be all accessible through your respective back ends. It sounds ambitious but I think a little bit of awesome.