(Yea, fiction, that is the only place where rape stories should be found...)
A little electrical stimulation should do the trick...
There are muscle twitchers, or shock devices that could be used here, control the voltage
and you can get anything from tingle to ahhhhh to eeeee to ouch to AAAAAAAAAAAAAAAA!!!!!
1: a probe in his ass, and one it hers, and the results should be "shocking"...
Now, a blow job, sex, or any contact will be stimulating... Could have him covered by a
rubber sheet, or in a rubber suit, with just the "interesting" parts exposed...
2: For if she does not want to partake... He is the only one with the probe, or contact,
and she wears a rubber lined metal glove... Now, where ever she touches... well, you get the idea...
... A hand job woild be an interesting experiance...
3: one contact around the cock and balls, the other around the cock above the balls, or around the head...
Add a condom, or 3 or 6... if she doesn't want to be shocked.... then ride the result. If the voltage is controled,
(and it should be...) she should be able to make him hard on command...
This could work it's way into "play" if the voltage is kept low enough...
But I think the only way this could be tested, besides kidnaping a stranger, is to use a very gay, and willing, test
subject and see if he can be stimulated this way...
Or maybe a regular sub that has been tied and over stimulated (read as "well fucked") and ready for release,
then the dom says "OK, now for a test... Let's see is what I read realy works..."
