Spray the bowl of a slow cooker with non-stick cooking spray.
Place chicken breasts in an even layer in the bottom of the slow cooker. Sprinkle taco seasoning evenly over the chicken then top with diced tomatoes or salsa. Squeeze lime juice on top of everything. Cover and cook on high for 4 hours or low for 6 to 7 hours.
Remove the lid and shred the chicken with two forks. Serve with tortillas and your favorite taco toppings.
*Nutritional information is an estimate. Please consult a doctor or nutritionist for the most accurate nutritional info.