Any recommendations for smartphone apps?

Have any of you used a free smartphone app in test preparation?

I downloaded freerice to see if it might be a good vocabulary builder, but it won’t work on my device. The kid has been playing on Khan Academy app all summer long, mostly when I forced him to.

I was wondering if anyone had experience with other apps that they might like? Is there anything more gamelike or actually fun out there?

I tried using a smartphone app, but honestly speaking, none of them were very helpful. The first problem is that with reading questions, the passages are super long and frankly hard to read/refer back to on a phone. I did try Daily Practice for the New SAT from College Board, but the only helpful part was writing (reading had long passages, and math I needed pencil/paper). I was honestly better off just using Khan Academy on the computer.

If anyone does have a fun/helpful app for the SAT, I’d also love to know.