@farmerman,
The only companion planting I've heard of with toms, is marigold. This supposedly keeps the aphids at bay, but for the past three years the dreaded blight has got the tomatoes before the aphids had even arrived, so I have no evidence to show one way or t'other at the moment.
Regarding blight, the frenchists in the family always poke a stiff piece of copper wire through the stem (once the plant is big enough to withstand it), about two inches above the soil line.
They assure me that it always works, but I suspect they have warm and dry enough weather to keep blight away in the first place.
I've tried it this year, and fingers crossed, so far.........