Cook pasta according to package directions, omitting salt and fat. Drain pasta in a colander over a bowl, reserving 1/2 cup cooking liquid.

Heat oil in a large nonstick skillet over medium-high heat. Add onion; sauté 3 minutes or until tender. Add tomatoes and 1/4 teaspoon salt; cook 2 minutes, stirring occasionally. Add shrimp; cook 2 minutes, stirring frequently. Add pasta, reserved 1/2 cup cooking liquid, 1/2 teaspoon salt, half-and-half, and pepper; toss well. Cook over medium-low heat 3 minutes or until thoroughly heated and shrimp are done. Add arugula; toss well.