Having the option to have bendy rubberized limbs in a character rig can free up animators to create some great poses. Adding that spline rig functionality into character rigs can be more involved that you once imagined. Certainly there are more than one way to create a spline rig.
If you want to dive into what is involved with one, there are lots of tutorials out there. Adding another to that list is 3D Rigging and Character Artist Alex Mann. Alex shows how you can create a dynamic and editable cluster for a spline rig. The interesting part is that the effects are controlled through a Maya Ramp Node. There are lots of great tidbits in here. Even through it runs a bit long, the video is well worth the watch!
You might remember Alex Mann, as the guy who made the Shelf Building Rig in Maya using the Mash motion graphics toolkit, a few months ago. You can revisit that post here.