Stretch click comes with a conductive rubber band and alligator clips.
Make a 21st century slingshot with Stretch click - a board that measures stretch forces of a conductive rubber band attached to it.
This is a very simple click board; the point is in the 1m rubber band that's included in the package. Impregnated with carbon, the rubber band has about 130 ohms per cm of resistance in its relaxed state. The resistance increases as you pull on it.
Depending on how forcefully you want to pull on it, the click has connecting pads for alligator clips as well as screw terminals for a more secure connection.