Hi,
I use this app a lot. It's one of the best book tests you can perform without carrying books or magazines around with you.
Also, there are a few clever ways to justify everything. I actually go into Wikitest from another phone effect called Cipher by Ellusionist. If you own both you'll see how you can go from one to the other, as you have the option to use a calculator on your phone in both tricks.
I'd say it's a must have effect for any performing magician.