The folks at 2.1 Films have just released an iPhone Film Calculator. From the description:
Film Calculator has three basic functions:
Length & Time Converter: This function allows the user quickly convert length to time and vice versa for a variety of film stocks and speeds. Choose from Super-8mm, 16mm, 35mm or 70mm stocks and preset frames per second rates (12, 24, 25, 48) or enter your own. Then enter the time and you'll get the length or enter the length and you'll get the time.
Hard Drive Storage Calculator: Select a format and enter a time and this function will tell you how much hard drive storage space you need. Dozens of formats are included. Contact us to request more!
Script Supervisor's Assistant: This function provides a stopwatch that counts both time and length. Select the stock and frame rate and then operate this like a regular stopwatch. Saves scripty's from having to use a calculator at the end of each take. Always know exactly how much you've shot on a reel!