In a small saucepan, bring millet, 1 tsp. olive oil, and 3/4 cup salted water to a boil. Reduce heat and simmer, covered, 20 minutes. Remove from heat and let stand 5 minutes.
Meanwhile, zest 1 1/2 tsp. peel and 2 tbsp. juice from 1 to 2 lemons. In a small bowl, whisk together zest and juice, remaining 2 tbsp. oil, and the salt.
Put millet in a serving bowl. Pour in dressing and toss gently. Add watercress, mint, onion, and shrimp, and toss gently to mix.
*Buy in boxes or in bulk at well-stocked groceries and natural-foods stores.
Note: Nutritional analysis is per serving.