There are many after-market automotive (car) cruise controls on the market globally. Many of them are end-run products sold very cheaply in auto stores, but the late model, sophisticated ones are quite expensive - not much different to our bike-specific, after-market cruise controls, which are much easier to fit.
Older car cruise controls typically use vacuum actuators, while later model units use electric actuators.
We have searched the world for a suitable stand-alone electric actuator with failsafe functionality, but have not found anything suitable for motorcycles. We use an electric actuator in our ATV and tractor range of products, but they are too big and too heavy for motorcycles generally. We fitted one to a Harley Davidson FXS and it worked well, but the mounting bracket had to be very heavy to support it and we felt that it was not very attractive for the cruiser market, which is so sensitive to aesthetics.
Consequently, we have an on-going project to develop our own electric actuator, but there are thousands of hours left in design, development, testing, eu-type approval, etc. before it will come to market. We expect it to take about three years.
Also, you would think that after 50 years of cars being fitted with cruise controls, that automotive cruise controls would be safe. We assumed so when we started our business in 1997 and our suppliers assured us that was the case. In 1999 to our dismay that was proved wrong when high voltage electrical spikes caused one of our adapted car cruise controls to fail in a dangerous state - the chip locked up as it was opening throttle and the bike immediately pulled full throttle. It took about 2 seconds and nothing the rider did would stop it! (Except turning the bike off - which he didn't have the presence of mind to do, in the emergency.)
That event drove us to develop our own computer and software to ensure it could never happen again. Moreover we developed our CruiseSafe product and retrofitted the kits that had been sold.
If you value safety, performance, reliability and support - give our product serious consideration. Yes it is expensive, but we spent $1.5 million developing our own software and hardware which is the ONLY after market, EU-Type Approved motorcycle cruise control in the world. Read the product reviews on the site at the bottom of each product page. You will be convinced not by me, but by our customers, that our cruise control is the best value accessory you could ever purchase.