I have seen, but never tried the i-cord cast on, i-cord bid off and applied icord. I have knit yards of icord for purse handles and drawsrings and even icord ribbon necklaces. But I've never seen or used this technique before.
The built-in i-cord is attributed to Elizabeth Zimmermann which is why I say it is something old. I think that one of the things I love about knitting is that there is always something new to learn. I'm thinking I may never make a plain garter stitch scarf again. The picture above is the beginnings of the scarf made from a varigated worsted Mainsatay yarn I got at WalMart for $4 for 16 ounces. I like the way it is turning out.
I can see lots of possibilities for this. The front edges of a garter stitch baby sweater for one. Panels knit with this edge would be really easy to sew up into an afghan. I want to experiment with this edging and an i-cord cast on and bindoff too. It is amazing how one small "new to me" technique can get you thinking. I want to experiment with this edging and different stitches for the middle section.
Since I googled and found this in other places on the web, I don't think EZ will mind me sharing her stitch.
Cast on desired number of stitches. Knit across to last 3 stitches. Bring yarn to the front and slip last 3 stitches as if to purl. Repeat on every row. It takes a bit (a couple inches) before the i-cord looks just how it should but it is a beautiful finished edge.