I found this recipe. It's called "Weight Watchers Easy Tasty Frozen Pie". It has two ingredients.
You need an 8 ounce (226.79 g) container of fat-free Cool Whip (or another brand of whipped cream type dessert topping) and one 6 ounce (170.09 g) container of light yogurt of any flavor. Mix those together and pour into a pie plate, with or without a pie crust, and stick it into the freezer.
I haven't tried it yet. I'm putting it here so I remember where it is. Sounds like it would be perfect for summer! If I like it, I think I will be making this pretty often.
Here's a link
with a picture and the nutritional information.