oh rita, what a great idea - good luck.
one of my favourite quilty apps, is "Fabric Stash" with it you can take pictures of your fabrics (or assign pictures in your picture data base) then there is space to enter the type of fabric, the colors, name, manufacturer, quanity you have incl. measurements in either metric or imperial, there is a space to enter its location, notes and even to assign it to a project. when i got my new fabric shelving this summer/fall, i took the opportunity to sort and refold all my fabrics, and they are now all photographed and entered into this app. makes figuring out if i already have this or that a breeze when i'm at a fabric store (i tend to buy similar things again and again).
For Calculating Fabric (blocks, binding, etc. etc.) either in metric or imperial, i like Robert Kaufmann's "QuiltCalc" App.
"BlockFab" is also quite interesting giving some basic block patterns with colour and combination ideas as well as a fabric calculation guide for the required patches.