Since Jaime and I are in this class as total beginners, we decided to take on something that was simple enough that we could tackle it but that would still be a technical challenge for us. Hence we chose to make a calculator with a slight twist. Besides planning a well-designed UI for it, we want to give users the ability to tag results as notes. We figure that this added functionality will allow people to figure out how much their groceries total is and tag it as such, or how much a friend owes them, etc.
We will be working separately but in parallel and we think that solving the same problems will let us help each other out when we come to any tough spells in development.