Latisse is bimatoprost, that is the same medication as the glaucoma drop, Lumigan that is formulated to lower the intraocular pressure. For many years, ophthalmologists have seen patients using Lumigan produce darker, thicker lashes. This is the basis of Allergan's repackaging of the same drug into Latisse.
So, Latisse will most certainly work to thicken and darken the eyebrow and and lower eyelid lashes.
However the caveat is that the skin will also become slightly red and have increased pigmenation in these areas as well. If you look at the photos on the Latisse website, you can see this increased redness and pigmentation. However, some may like this look, as it may simulate the look of eyeliner.
The next caveat to using Latisse off-label on the lower eyelid is that when Latisse gets onto the ocular surface (which occurs more easily with application to the lower eyelid), several things can happen. First, the eye pressure can be lower. This effect is harmless in virtually all patients. Secondly, and more importantly, the drug can actually enter into the eye and increase the pigmentation of the iris. A person with light brown eyes can darken to dark brow. At most risk would be patients with blue or green eyes, who might darken to a hazel color. Finally, patients who have ocular surface disease or are conteplating eye surgery such as cataract surgery or LASIK may actually increase their risk of complications if they have Latisse entering the eye.
The bottom line is that the off-label uses can be powerful, beautiful results, but check with your experienced provider first to clarify if you would be a good candidate or a more risky candidate for these other less desireable side effects.