Nothing works better than the human brain for testing and adjusting the SWCG's output.. Kind of like self-driving cars.. They work great... right up to the point of the crash..
There are systems, like the IntelliChem, that adjust the FC, but they are not something that we recommend, as in the end, they turn out to create much more effort and trouble than they are worth.
It does not take much effort to get a feel for the amount of FC your pool uses and adjust the SWCG's output.. I might change the output of my SWCG about 5 or 6 times a year. Mainly at the start of the season and at the end of the season..
Just don't try to micromanage the output by trying to hold the FC at a very specific number.. It never hurts to go a little high after a cloudy day.. I always try to maintain my "target" FC or higher.. This means that if the pool uses more FC on a particular day, I am still nowhere near my minimum FC.. A cliff that I never want to fall off.
The short answer is that there's nothing available to measure FC. You can measure ORP but this is at best an imprecise guess of FC and is affected by a lot of other things in the water that make it extremely unreliable. So it doesn't prevent the need to manually measure FC about as often as you would otherwise.
I do have a SWCG that has another attached unit that measures and maintains FC and pH. It was already installed when I bought the house.
Search for "Puresilk Chromatalyzer" this is the older version and no longer made.
This unit uses photometer to measure and you can set a set point to control the FC by turning the output ON and OFF to the cell and keep the pH around a certain level with the attached peri pump.
When it works it works ok but it does have issues and you do have to keep an eye on your water with manual testing. I do weekly checks.
The last reagent bags made the FC READ 2ppm less and pH is always 0.3 less.
Like a lot of domestically price equipment it will play up and the cost of replacing parts is expensive. It also has it limitations especially if you are keeping your levels at the Recommended TFP way. The FC has a max set point of 5ppm (it does measure upto 10ppm) so if lile to keep your FC above 5 then you will have manually dose anyway.
I'm happy to maintain mine but I'm also double checking it's reading by manually testing weekly.
In short as the other replys mentioned you can't beat manual testing and you should do it anyway doesn't matter what automation you have. Once you have your SWCG dialled in you still check the pH and TA so why not spend another 60 to 90sec and check the FC?
I hope this helps.