How can I learn Spanish on my iPhone?

Hi all,

I’m traveling for 3 months, of which the last month will be spent in South America. I’m thinking it’d be good to pick up some Spanish before then.

I’m looking for the following:
* Either great Spanish lessons in MP3 format
* Or even better, an awesome iPhone app (more interactive, exercises, etc). However, I’ll be out of cell reception, so it has to work without an internet connection.

Any suggestions much appreciated!

-Nick

PS: I posted a similar question about my Kindle, but that doesn’t seem like the way to go :)