Here's a video of my hacked Inchworm cruising along upside down, suspended from some nylon string:
But how does the inchworm normally work? This article has a general overview, and the video below is a good example of normal operation.
Step 1: Parts: Rubber band, coat hanger
Get a metal coathangar, and cut two pieces about 10" long. Ben them into Ws as show. Make the outside arms of the W about 2 inches long, and the inside arms ( the upside down V part) about 3 inches long. When you suspend your inchworm from the string, this will position the string right between the bottom of the inchworm's two feet.
Step 2: Attach coathanger Ws
Make sure the tines of your W stick close to the inchworm's legs, so that the edges of the legs keep them trapped and stiff.