How to tell if a carpeted floor is level enough for laminate flooring?
Lie down and eyeball it. It's easier to see if you are right down on the surface. Someone in the business of laying floors might have developed a better eye than you (if they miss it, it costs them money) and not need to lie down.
Shoot a laser pointer across the floor - either skim the surface looking for discontinuities, or lay it on the floor and check its height with a ruler as it goes across the room. Easier if you can get the start and end adjusted to the same height. A hump will be a place where the beam height above the floor reduces; &amp;/or where the beam won't make it across the whole room if it's right down at floor level.
Choose a long straight board, and set it on edge on the floor. If you find a place where it rocks from end to end, that's a hump. Check that the board is really straight by making sure it rocks about the same on both edges (a warped board will rock on one edge, not on the other - a straight board on a hump will rock on both edges)


If you want to install a wood floor over a hump, wood parquet can be much more forgiving. I don't know if the laminate folks have entered that market, but it can be quite affordable in real wood.