Custom timing Application for OS X

I have a program for personal use that I would like written for the OSX Platform. In basic form, the application would allow a user to input 4 numbers and choose an amount of time (days/hours/minutes). Once started the program should be able to be closed and when opened again check the time (other words, it shouldn't have to be running all the time in order to keep track of time). There needs to be some type of encryption or scrambling, so that no one can see the 4 numbers until the time is completed. I would like for there to be options to show amount of time remaining (either true time or an incorrect time for added suspense). I have some sample sketches of what I would like the interface to look like and some more details on available options while the application is running.