Bump sensor with variable resistance

OK, many months ago, I ran across a clever design for a robotic bump
sensor.   It used a flexible rod,
bent into almost a complete circle around the robotic chasis.    The
rod was constructed so that when pressed
anywhere along it, the resistance being seen by the system would
change in a way that would
allow it to calculate where the touch took place.  So, rather than use
16 touch sensors, or some other
number, you ended up with the ability to tell where contact occurred
anywhere on the ring.

Sigh.   I cannot remember the details, though, and I cannot find the
article.   Heck, I cannot even
remember if it was online or in Servo/Nuts&Volts/Robot/something
else.

I am hoping this brief description jogs someone's memory enough to
give me a pointer.
Any thoughts?

Thanks,
kenny