The coolest app I saw at ETech, by far, was Dopplr, which Matt Biddulph kindly demo’d for me. I wanted to clap with glee. You really have to spend enough time on airplanes to be able to repeat the safety instructions from memory in order to jump up and down about it, but I’m in that group and I love it. I have a whole category of friends I call my “airport friends” since I’ll be changing planes in Chicago and run into them, though neither of us live there. Dopplr made me so happy because, first, it makes those serendipitous meetings its special talent, and second, because it just feels so right as a web application — like a tool that fits perfectly in your hand. Cheers, Matt and company, for getting it so right, and thanks for the invite. For the rest, take a peek at some screenshots. (They’re rolling it out GMail-style, so be on the lookout for an invitation.)