I bought two remote shutter releases, I think its Pixco brand from China. Works well. The one I actually want to use for long exposures, although I can see myself modifying it into a nice, custom enclosure which will also house the intervalometer.
I haven't done anything of the sort yet. What I can tell you is that there are three plates in the unit, first two touch and you get the "half-press" function, those two touch the third and you get shutter release. There's two resistors, and if I remember correctly, the one resistor goes between the first two plates, and the second resistor between the second two.
Wish I can tell you more but I have too much on my plate at the moment to focus on that. Hope you get some info regarding. I hope to finally get to this in the next two to three months. I am also thinking of a pan-tilt head with slider. Though I want my pan-tilt head to have the added function of being controller real-time via a joystick of sorts, like a turret gun 8)