My first idea stays the same, making an online food ordering system that works over wifi. I need to think about how to differentiate my product, what is new with this, and how to test it.
A web platform aimed at helping people learn/practice math. Using a template, it would generate math questions, and allow people to try to solve them. It would also provide step by step solutions for people. This would be especially applicable to calculus. There are APIs that help with this, at least some open source.
A time tracker app for TAs, who are currently logging in their hours on a Google spreadsheet. This site could allow TAs to clock-in and clock-out, take attendance, and also show them how much they worked in each pay period. The app would also update the currently existing Google sheet with the new logs. This can also be packaged in a way that others can also use it.