The 3.5mm jack breakouts have arrived, and been promptly soldered up.
Doing some extremely simple testing, I can already pulse, fade, and random the attached device. So from this point, some serious software design needs to be done, and some reading up on actual arduino coding styles. I'm new to this, so I'm expecting the first iteration of the software to be pretty terrible. After all, "plan to throw one away".
I've just ordered a couple more vibrators with 2.5mm plugs to use for testing. I'd like to try and work out the average minimum voltage required by something attached to the device, and maybe include a way in code of setting this minimum through the buttons.
On to ideas about batteries. This project is required to be battery powered (according to DA RULEZ) and it will be, just as soon as I figure that part out and order the parts. I'm leaning towards cheap usb emergency phone chargers at the moment, as they output 5v and are cheap, with all charging circuits built in.
EDIT: Look a video! It's not very good but it shows this is an actual project!video