The Halogen fog light that comes with the car and all standard replacement bulbs are 55watts. I don't believe it would be wise to go higher than that. You would most certainly blow a fuse. If you really want yellow fogs, just get bulbs with lower watts or install an HID conversion kit with 3000K bulbs. I think those come in 35w or 55w.
To your second question, the only device I've seen that does this is:
http://www.kptechnologies.com/products.php#/12
Not sure how well it works though.