After taking a couple of big, deep breaths (and a couple of big, deep glasses of wine - thanks Kristine, for drinking in my honor, by the way), I got a bit of perspective and decided to move forward with my big, big idea. But it will be from a different tack.
My original idea was a bit of a two-'fer: two internet tools that worked in tandem. The other company I mentioned has only beat me to the punch on half of it. So I'm seriously considering pushing forward with the other tool and pursing either a partnership, collaborative effort, or creating a tool that can "play nice" with others already in existence.
Onward and upward.