Steve Kaufmann recommends flashcards with the answer and question on the same side. I did find one iPhone app that was good and done just that. But it had no pictures or audio and it was discontinued.
My ideal app on each screen would show the word in Spanish + English translation + picture + audio. The audio would automatically play when changing to the next card. The key is speed.
If I am unable to find such an app I will develope one. I know there is anki but I don’t know how to configure it as it has far too many features. And out of the box it does not do what I want it to: if it is possible at all. It would also print out flashcards.