Combine the flour in a plastic bag with 1/2 teaspoons salt and 1/4 teaspoons pepper. Add the chicken pieces, and toss to coat evenly with flour.
Heat the oil in a dutch oven over medium heat. Shake the excess flour from the chicken pieces and place into the hot oil. Cook until browned on all sides turning occasionally, about 15 minutes. Pour in the water, cover, and reduce heat to medium-low. Cook 30 minutes.
After 30 minutes, stir in the onion and bell pepper. Cook and stir until the chicken is longer pink at the bone, and the onion is tender, about 10 minutes. Pour 2 Tblsp. of the reserved peach juice into a small bowl, and set aside. Pour the remaining peach juice into the pot along with the soy sauce and vinegar; bring to a boil over med-high heat. Dissolve the cornstarch in the reserved peach juice, and stir into the boiling sauce. Cook and stir until the sauce thickens and is no longer cloudy, about 1 minute. Stir in the peach halves and chopped tomatoes. Cook and stir until the peaches are hot and the tomatoes are beginnning to fall apart, about 5 minutes. Season to taste with salt and pepper before serving.