Ringtone remote installer

Ok I finally got the program finished. Now I need to set up a website and figure out the best way to market it. This could be big. Imagine calling a friend and changing his ringtone without his knowledge. I've got it set to only use the installed ringtone when called from the number that was used to install it. I envision some embarrising phone calls inturupting meetings. I wonder how much I should charge.