I don't know if they still sell the CIU separately or not.
I just crawled all over their site. I found the CIU for both single- and dual-spool versions, something to do with the cable arrangement, like splitting into two. I'm guessing the ST1100 would take the single spool type. Their 1100 kit comes with a speed sensor coil and wheel magnets, so it doesn't read ignition pulses, unless that's something new.
Their vacuum servos, which are probably Audiovox units, are being superseded by electrical ones, which are
not duplicates of Rostra units. Their servo is cylindrical, while the Rostra servo is a rectangular box. They do have bike-specific speed sensor coil brackets, not a big deal to me; the one on my Nighthawk would be unnoticeable if I painted it black.
On my Nighthawk, I didn't need anything but the thin wire loop that I put the barrel of the pull cable through, so it shares the pulley wheel. I've read that the ST wheel is solid and can't fit the loop without machining, and that a popular DIY interface is an arm screwed to the wheel. That also gives the servo more leverage and probably smoother operation.
To me, the greatest plus about their kits is the control panel, which is clearly made for bikes, is also sold separately, but requires a separate mounting bracket and, if it matters to you, a separate back seal. For the ST1100, there's this:
THE ELECTRIC SERVO UPGRADE KIT MUST BE PURCHASED WITH THIS PRODUCT, which tells me the price is going to break US$1K for everything.
In my opinion, as a DIYer, that is just too steep compared to a Rostra kit at around $200, plus a coil kit and the handle-bar switch I posted earlier. The switch has up (acc/res) and down (dec/set) arrow buttons, and a bar on the center button I wired as a cancel with a tiny relay to ground the clutch-switch wire. A resistor dimly lights the kickstand light when set.
My servo is in an empty space behind the transmission, above the swing-arm pivot and below the airbox. The throttle cable points to the right and curves up, toward the front, and then down, the outer tube clamped to the bike's pull-cable's outer tube. With the above-mentioned wire loop around the cable barrel end, secured with a baby nylon wire tie.
I used four magnets, attached to the chain side of the rear wheel hub with a long wire tie made from four, and the coil is mounted to the tip of the swing-arm with the bracket bent in an L so the coil bolt head actually faces the front of the bike. Cars use one magnet for a rear-drive drive shaft or two for a FWD axle; I used four for greater "resolution" reading speed.
About the ignition connection: according to the Rostra instructions, this signal is used to prevent the engine from over-revving in case you bump an auto tranny into neutral, but not for maintaining speed. Since I connected the neutral safety wire to the bike's neutral light, and I connected to both the brake-light and clutch switches, I didn't worry about the tach wire.
It took me one long day to get it in and wired, and about six attempts to get the DIP switch settings just right. It works just as well as a factory-installed cruise control in a car, as long as I keep the engine RPM from dropping too low up a hill. It maintains speed on the highway like it outta. Instructions (for cars) here:
http://www.rostra.com/manuals/250-1223Form4565G.pdf
For controls for the Rostra, there is a write up somewhere that uses the ST1100 Police switch - which is weather proof - to control the Rostra. Reg Siemens was the first to do that and it makes a really nice setup (the 1-2-3 part of the switch). A lot of folks go with the Audiovox because it is so much cheaper and just seal up the control to try to make it weatherproof. Good luck on whatever you chose to use.