I doubt if it would help much, because the trajectory of a blowgun dart is very ballistic, compared to a straight laser beam. I don't even think they work that good on firearms, at least not a distances beyond 10 yards. A laser sight might be OK if you are never going to shoot farther than 15-20 feet, or so. I think beyond that, it would be useless. I normally practice at 10 yards, up to 25 yards with my CS Magnum blowgun.
I tried one of those peep sights that go on the end of your blowgun, and found it to be useless as well, because of the required hold-over. You pretty much have to shoot instinctively with a blowgun.
I may be the wrong person to ask, because, even though I do use sights on my crossbow and compound bows, I build and shoot traditional bows as well, and I absolutely hate sights on a traditional stickbow, as well as any kind of attached quiver. I also hate the little quiver attachments on the barrel of a blowgun. They throw my aim off. My blowguns are stripped, except for the mouth piece and a muzzle cover when not in use.