I planted nasturtiums near my cucumber, pumpkin, and rosemary to act as "bait plants" for aphids and spider mites. Plus, having the pest bugs is bringing in beneficial bugs like ladybugs and lacewings.
Good idea with the nasturtiums... I was really irritated this year to see so many aphids on them but I left the plants in place since I figured that kept the aphids from spreading to other plants. Didn't think about using them deliberately to "bait" aphids away.