Here’s an app I developed more than a year ago and has been on the app store for a year now with some under 1000 downloads without any advertisement.. word of mouth and usefulness of the app.
The App as described on the apps site: Stockulator is a calculator designed for helping you estimate and calculate your possible gain vs. loss when a stock price rises or falls. It simulates your entire calculations of number of shares, amounts etc.. and helps you project how much money you are going to make before buying or selling any shares.
Get the app: http://itunes.com/apps/stockulator
Help for using the app: http://apps.amplioslabs.com/stockulator/
Welcome to your ideas and comments.