Ringtone Director Presidential Edition (US$0.99) lets your iPhone announce incoming messages in voices that sound like that of US President Barack Obama or former President George W. Bush.
Using the app is simple. First, type what you want Obama or Bush to say, then you'll receive a link to an .m4r file via email. Install it as you would any other ringtone. You can also get an mp3 file for non-Apple devices. The Obama and Bush voices sound reasonably close to the real people, and, of course, you can have them say anything you want, funny or serious.
The onscreen directions are pretty straightforward. Type the text you want spoken; add some sound effects if you wish (like the Hail to the Chief music); and send it out for processing. To do that, you hit a button marked "action," but it wasn't clear if it worked because there is no feedback that the data has been sent. It seems an easy fix for the developers.
The app allows you to create 10 different ringtones; after that, you have to pay via in-app purchase for more. A $0.99 purchase gets you 10 more, and $4.99 lets you create 100. I would think the average person can get along fine with 10.