To stuff, here are some ideas:
Fat Free Cheese
Ground turkey or ground beef (ground beef is C2)
Crab Meat (watch out for added sugar) (Crabmeat is C2)
Really, your imagination for what to stuff these with is the best diet tool!
Core and remove seeds from the jalapeno peppers and stuff with whatever combination of ingredients you like. Once the jalapenos are cored, they are not hot, as the seeds are what contain the "heat."
Place on a cookie sheet and bake for 15 minutes at 350.
Note: Jalapenos are a C3 item; if you used this recipe using something else such as bell peppers, it could be a C1 or C2 recipe.