Simple Mac App Needed

The mac app that I'm wanting developed is really simple: Every 10 minutes I'd like the screen to go black and display a random line of white text (for 7 seconds only). Then after 7 seconds, it goes back to the windows, wallpaper, etc. And then it repeats, every 10 minutes ...but always pulls a 'RANDOM' line of text. The mac app will pull this random text from a text file (or something that can easily be edited by the user). That's it. Simple :) Let me know if you have any questions regarding this app. Thanks!