Place bacon in a saucepan and cook over medium heat until just beginning to crisp.
Add onion and cook, stirring, until softened, about 5 minutes. Scrape bacon, bacon fat and onion into slow cooker.
Add crushed red pepper, peas and 4 cups water and stir to combine. Cover and cook on low until peas are nearly tender, 3 to 4 hours.
Stir in tomatoes, rice and salt. Cover and continue to cook just until rice is tender and has absorbed all liquid, 1 to 1 1/2 hours. Fluff with a fork and serve.