I am a computer programmer and have been contemplating it for some time.
First of all the idea of a very long octopus like arm with a hand on the end is not currently possible. You'd have to have some kind of hand which is stationary, meaning you couldn't have a machine that grabs someone or allows them to struggle against the machine.
The idea of electic or vibratory tickling is out of the question. The primary method of tickling is via contact with fingers/brushes etc. In spite of what some "chinese cartoons" would have you believe, a feather machine would not tickle that much. Moreover a clit tickler is not really possible: most vaginas are not ticklish.
That being said there are some 3d printable robot hands in which each finger moves independently. What would be necessary is to at the tip of each finger put some kind of rubber nub or claw so that it has the right feel on the foot, then to have a machine which controls the hand.
In my mind the best way to drive the hand is via springs which cause the fingers to expand and strings which pull the fingers closed. The strings can be driven by a pulley system via an electric motor.
The electric motors can be driven on/off and at varying intensities. This can be driven by a device called an arduino or a raspberry pi. I prefer the rasperry pi because although twic the cost it is much simpler to program.
The only really difficult parts are these:
1. You don't want the hand to be so strong that it somehow damages the feet.
2. You need the patterns in which the fingers move to be diverse enough that the ticklee could not predict how they move. We would desire a large range of movement meaning you would need some kind of omni-angle rotor which can change the angle of the hand as well as change the height of the hand and to move it left and right.
3. This is among the biggest problems. Each foot is a different size. Lets say that you trained the machine on a foot that was too small, and that your hand was programmed to go for the toes. The lee might be able to just move their toes out of the way if the machine was dumb enough thus evading the machine. The ability of the machine to see a new foot and adapt to a new geometry is rather difficult. The way I see it, the easiest way to put the geometry of the foot into the machine is lasers that scan a model of the foot. If one uses lasers, it is necessary that the foot is given tight toe restraints that it stays in the same position. This is also true of the upper body.
All of the components to make something like this more or less exist. It is a matter of finding an investor who is willing to pay for the parts, a programmer who is willing to program it, and a volunteer who is willing to try it out.
For a machine that just tickles the soles, arches, and toes, it wouldn't need to be very large. Maybe about as big as a deckchair. For a machine that tickles the whole body you are looking at a very big very expensive machine.
There is a company that makes this sort of octopus arm for handling things in factories. Essentially some robot arms in factories can sometimes go haywire and then hurt the workers in this factory. So they have this thing which is kind of like a tiny octopus arm which is filled with air and the direction of the air can make it wiggle around. I think that this would be cheaper and more ideal than a 3d printed hand, however it is currently patented by that company.
I am more than willing to help consult with someone on how to program/build this thing. I am well capable of programming it, I just don't have the money to build it.
