The product is called the Counter-Weight, and it is indeed an invention by Pat Fleming that is sold through his site at Accu-Stats:
http://store.accu-stats.com/the-counter-weight/
I've had it for a while and I think it's a clever and useful tool. Even if you are very disciplined with CB frozen to the rail shots, I realized that when the pressure is on in competition I would miss shots when I was shooting perpendicular to the rail and especially when I had to bridge diagonally across the long rail.
The Counter-Weight adds significant heft to your shaft. It is a short solid tube of tapered and knurled metal with a ring on the outside to indicate which end points up. Inside are two rubber O rings that protect your cue from nicks or scratches. It easily slips on and doesn't slide around. With a simple twist it loosens and slides right off.
I was concerned at first that I would bang up my shaft, but after a day or two of practice it became second nature. After almost a year of use I have had no damage as a result of using it.
After a couple of months, one of the O rings came loose. I re-guled the inside of the ring with a little superglue and it hasn't come loose since.
I find the Weight to really help me prevent the shaft from flying up on rail shots, and it also keeps the tip going through the CB when jacked up. It has given me an added degree of confidence on these types of shots. I don't make them all, but I noticed that I've been making a better percentage of them. It is also advertised as helping on shots when you have to bridge over balls and also when slow-rolling balls, but I don't really use it in these applications.
Like I said, I've been using it for about a year and only a few guys have ever even noticed me using it. The best compliment I guess I had was when I was playing a guy and had a long, nearly frozen shot from the foot rail and had to draw back for the next ball. Using the CW, I jacked up and made the shot in the corner, and drew back a diamond or two to get perfect po on the ball and complete the runout. After the rack my opponent asked me what the weight was and if it was legal to use, and I told him, "Of course, Pat made it; it has to be legal." - To which he grumbled, "What the heck does he know?" lol.
TL;DR:
It's a cool invention from a great guy. It's a little spendy, but worth checking out if you have issues with rail shots.