1. PriceMaker calculator for tax and profits in wholesail and retail (for small businesses).
  2. Calculator for deployment of photo-voltaic solar panels
  3. Personal diet calculator

These can be installed to be used as "Apps", with an icon in home. To install, open the page of the above calculator in Safari. Click the  icon with  a box and an arrow. Select: "Add to Home Screen".  The App will be available offline and will automatically upgrade to new version when available. No need for the App store.