I rigged up an octopus similar to this about a year ago, it was for a 3dsmax rendered project in max but it can be modified in a way to work real time, it just depends on how you set up the final resulting skeleton. I'll dig through my files and see if I can get anything more specific, but here is what I remember doing.
For the webbing:
I had a few bones for each piece of webbing, these bones where position constrained to follow the final skeleton bones for the tentacles on either side. 50% to the left bone, 50% to the right bone mean it floats in the middle.
To pull the webbing away from the body and down the arms I would adjust the weighting between the position constraints to the next or previous bones in the the chain. I rigged up the weighting to a simple slider so it was easy to animate. I think I used reaction manger but I might of used wire parameters because I remember messing around with expressions... I'll have to go digging...
I also remember attaching helpers to the position constrained bones and skinning to the helpers so I could hand tweak the position of each bone in the webbing. This was helpful when I wanted to add some drag to the webbing.
For the tentacles:
I had 3 skeletons:
- Final Skeleton, everything was skinned to this. This was linked to helpers that where position constrained between the other two systems much like the webbing. Simple sliders adjusted which system the final skeleton would follow.
- FK, standard bones, fixed length bones no squash or stretch. Nothing speical, selecting all the bones in the chain and rotating them on their local pivot(the only way to animate) I could whip them around, curl and uncurl them.
- Stretchy bones that worked a bit like spline IK but the control points wouldn't slide off the end or travel to odd spots in the tentacle like spline IK tends to do.
At each bone pivot there was a helper that could be manipulated and each bone would squash or stretch as the helper was moved, leaving the rest of the points where they where. This made it possible to pick up the tentacle with sort of a ripple wave motion emanating from the body.
Because they squashed and stretched I got some great elasticity in the arms.
After I had rigged up most of the arms manually, I found a script written by Jason Labbe that automated setting up the stretchy bones portion of it. I can't find the script on the web anywhere so here it is
. Double click the first bone in the chain to select all the children and run the script.
For the noise:
I never implemented anything like noise, I guess playing around with noise controllers in the curve editor, would be the way to go but it really depends on what kind of noise you want.