You could very well use the efi fuse, but I would only use a low current draw relay, such as a reed relay, to trigger a standard relay.
Of course, this just adds more work, and it would be so much easier to run a wire from under the steering wheel area through the firewall and into the engine bay area. There are several rubber grommets to go through, use a wire coat hangar and push through from engine bay into floorboard area, tape your wire onto hangar, pull back, job done! Shouldn't take more than the amount of time I took to type this out!
And to make it even easier for you, as long as its there on your year, my '11 SR5 has a nice little grommet just to the right of the brake reservoir, its not even being used! Pop it out, stick hangar in there carefully and push in at a downward angle till you see it come out on the floorboard area.
As for wiring, look at [MENTION=65614]Antman[/MENTION] 's thread on the foglight mod, there's a few diagrams with color codes to tap directly into the wiring, or you can do an add-a-circuit at the fuseblock too.
