Hey everyone....been working on this script tonight based on an idea I had last night.
Still VERY rough....so it's in the "proof of concept" stage right now (ie...very preliminary)...but here's what I've got so far!
It's quite simple, even though some of the math is a little tricky.
Basically, you run the script on an ik chain point of your choice, and it will automatically animate the legs. It also does it real-time and on-the-fly, so NO keyframes are created at all during or after the process (and you can literally drag your "bug" around in the viewport with your mouse and the legs will walk with it as you drag!

)
The theory behind it, is that a position script checks to see if a leg has stretched out, and if it has....it moves the leg's IK chain point back into its original position (relative to whatever object the leg is linked to)...thus giving the illusion of a leg travelling, or "walking"....still no movement in the up-axis...but I'm sure that's soon to come
Anywho...here's a test anim with a centipede. Obviously very buggy (lots of legs jumping out of place, some legs don't work well and obviously they don't bend very far before taking another step...)...but it's at least working!
http://www.tysonibele.com/Main/Scripts/Legs/legs1.avi