Calculate your net or take home pay within different time frames.
Calculate how much is your net pay or take home pay after tax was deducted and see how much it is in different time frame. For examples, if you make 100,000 annually, you can calculate how much you will get in month, week, day, hour, minute, or even seconds.
I suppose it would be useful for someone... but not for me.
Cons
This is basically a glorified spreadsheet. Input one number, and have it displayed multiplied or divided by 12, 24, 26, 52, 365, etc. I was able to reproduce its function in excel in about 12 mins.