Well "electric shocks" and "vibration" ARE stimulation.....

There are reportedly people in the east who can ejaculate by mind only and this is well documented. There was recently a woman hypnotist who posted several self-hypnotism recordings on the web which, if practised for a few days, apparently give one the ability to reach erection, orgasm and ejaculation without any direct physical stimulation.

Electro-stimulation has been used to 'collect' semen from both animals and human paraplegics. I think it is now banned for animals as it is considered to be cruel. This method is carried out by placing electodes inside the rectum. Able bodied people aparently find it extrememly unpleasant.

There are several machines which will bring a man, or animal, to ejaculation without any help or co-operation from the subject. Some of these are used in collecting semen from horses and bulls with various degrees of popularity depending on country etc. In Europe it is more usual to use 'teasing' methods for animals by means of a llive female and an artificial vagina.

A machine for human males which apparently works very well and requires no action other than to 'penetrate' it, is the 'Venus 2000'. This is essentially a captured air system which causes an artificial vagina to travel up and down the penis. It is very expensive but aparently very effective and does not even require an erection.