Your grades are yours, thus all of them are stored on your device.
gradebooklet will be free forever. Sure.
Designed for everyday use.
You define which modules you want, to save your grades.
All your Exam's and grades are stored at one place. Therefore you will have better control about your current average grade for each module.
gradebooklet is still in development, this means, with every update it receives, it will get better. Install the app now, and create your gradebooklet.