If you favor the Weight Watchers method of keeping your weight under control, you might appreciate this WW Points Calculator.
WW Points Calculator is a simple app in the extreme - there are no configuration options or, in fact, options of any kind. You launch the app - which is a horrible color by the way - and enter the calorie, fat gram and fiber content of the food in question. Hit Calculate Points, and you'll get the value in WW points.
As WW Points Calculator requires you to enter the nutritional information of foods, it is probably easiest to use with pre-packaged foods or items where the nutritional information is clearly printed. I did a quick check of the accuracy of WW Points Calculator against the official Weight Watchers website, and the calculations seemed pretty accurate.
WW Points Calculator isn't going to blow your mind, but if you follow WW, you might find it useful.