The website they built is called ITA Matrix (http://matrix.itasoftware.com) and it's still available today even after Google acquired them. It's the most powerful flight search engine out there.

That sort of graphing of time intervals goes back at least to the Gantt chart:

http://en.wikipedia.org/wiki/Gantt_chart

Maybe Hipmunk saw the one in the presentation, but it wouldn't be surprising if they had not.