Most homes with a central ventilation system have, attached to the main duct trunks, rectangular air grated registers (otherwise, it's just blind ducts, and that's stupid).
These registers split the air into two directions - left, and right. That's pretty much it.
You can by vaguely curved air
deflectors which redirect the air forward. But forward may not be the direction you want the air to go - what if, say, the register is across from the crib? Then you're either freezing, baking, or dehydrating your baby.
Additionally, these deflectors usually don't fit well, and often leave the front (or back) of the register uncovered, reducing the deflector's efficacy.
So instead, I propose this:
A clear plastic frame, which contains four square slots, or rails, into which four curved air deflectors can be inserted. Because they are square, these deflectors can be aimed in any cardinal direction. Various angles of deflection could be offered as secondary sales items.
Like current deflectors, this frame would be held on with magnets. But because the frame attaches to the air register on all four sides, it can fit more snugly.
The item would be manufactured in a variety of common sizes, and in a variety of colors.