I wouldn't use those in your headlights. No matter how bright they are, the beam spread is going to be horrible, probably worse than HID's. The reason dedicated LED headlights are just showing up on newer model year vehicles is because of the amount of work that is needed to focus the beam properly.
A kit like that may work decent in the fog lights because of the wattage, but keep in mind that the wattage does correlate to heat output to some extent. Don't want to go melting your fog light housings.
It is confusing to me as to why they require ballasts though, and the description makes me laugh.
- Super Bright! (Brigthter than typical HID Kits)
In spite of that, the ballast says 1800 lumen (per bulb), whereas most 35w HID's put out 3200 lumen per bulb. Shady marketing right there.