I actually tried building and selling these things, a project that was something of a flop--in part because of some design shortcomings, and in part because I don't really have the money or resources to do something like this properly. I called the gizmo "Symphony," and lost money on the project.
The Symphony design actually started as a phone-sex gadget; in the original conception, you'd plug the gizmo into your phone jack (remember those?), plug your telephone handset into the gizmo, and talk to someone on the phone. If your partner pressed buttons on the touch-tone phone, he could switch the sex toys plugged into the gizmo on and off.
For that reason, the Symphony works on DTMF--the shrill noises you hear when you push buttons on a phone. Basically, it's nothing more than a DTMF decoder (that recognizes the buttons), a series of bi-stable latches, and three relays. When you push the buttons on the phone, the relays switch on or off, depending on which buttons you push.
In fact, there's a schematic of the Symphony below this cut
The HT9170 is the tone decoder. The 7402s are arranged as three bistable latches. They drive three mechanical 5-volt relays via three VN0605 TTL-level MOSFETs. The VN0605s are tricky to find in small quantities; anyone who wants to build one of these to tinker with might want to replace the VN0605s with a 1K resistor and a 2N2222 switching transistor to drive the relays.
Or replace the transistor/relay pairs with a solid-state relay and be done with it. That's the right way to do it, though the solid-state relays are a bit spendy, which is why I didn't do this when I thought I'd be mass-producing these things.
It occurred to me early on that generating DTMF in a computer is trivial, and that this device could be controlled easily by a computer. And thus, Symphony was born.
The computer version of Symphony has a lot of shortcomings. The biggest of these is that each sex toy has two states: on or off. That's it. No speed control.
Symphony has been a dead project for about five years now. I keep thinking of revisiting it in the form of a much more sophisticated, USB version with speed control and all kinds of other neat stuff. I also have been thinking about publishing more detailed information, including the PCB pattern, sample software, and stuff like that in the "do it yourself sex toy" section of my Symtoys Web site.
A little while ago, I posted a journal entry about creating a sex toy guaranteed not to get the user off. I've seen plans for simple versions of such toys; basically, they're vibrators that switch on and off at random intervals, never running for long enough to cause an orgasm but always running just enough that they can not be ignored. A random-number generator connected to a relay does the trick.
Recently, I've been having some online conversations that have revealed to me a need for an Internet-enabled toy that's designed to torment and tease someone without letting her get off, preferably over the course of extended conversation. And my mind went back to the Symphony project, and...
Okay. So Symphony in its current incarnation isn't a very good sex toy; it's too limited. However, what about adding more "smarts" to the client chat software? What I've been thinking is this: The client software can contain a random number generator, possibly weighted by several variables controlled by the host. So in addition to "on" and "off," the host can put the sex toys connected to Symphony into "torment mode," where they run at random, varying intervals, whose parameters can be adjusted by the host for...err, maximum effect.(I can't simulate speed control by switching the toys on and off very rapidly--essentially, using a square wave as the power source and varying the frequency and duty cycle of the square wave to vary the speed of the motor--because the DTMF tone decoder takes a while to respond. The minimum tone duration is pretty long--about 250 ms--so the practical limitation on the rate at which the toys can be switched is only 3-4 Hz.)
So what you'd get is a chat program that could control sex toys designed to drive your chat partner absolutely stark raving nuts, without letting her come. Since the device permits only on/off control of the sex toys, might as well turn that bug into a feature!
I still have about eight populated Symphony boards kicking around somewhere. I'm sore tempted to dig them out and start tinkering with them.
Yes, I use my powers for evil.