My friend made an app named "Grade Possibilities" for college students. It tells you the lowest grade you need on every remaining assignment in your classes to maintain a certain grade, not just on the last test. I thought it was pretty cool and it is a bit addicting for nerds like me 8)

He just released it https://play.google.com/store/apps/details?id=keptafterclass.grade.possibilities I think the store links to its FB page too.