Linguists believe that kids require interaction to learn languages. Here's an interesting article about it:
http://www.linguisticsociety.org/resource/faq-how-do-we-learn-language
The first part is the most interesting for you:
Although parents or other caretakers don't teach their children to
speak, they do perform an important role by talking to their children.
Children who are never spoken to will not acquire language. And the
language must be used for interaction with the child; for example, a
child who regularly hears language on the TV or radio but nowhere else
will not learn to talk.
Children acquire language through interaction - not only with their
parents and other adults, but also with other children. All normal
children who grow up in normal households, surrounded by conversation,
will acquire the language that is being used around them. And it is
just as easy for a child to acquire two or more languages at the same
time, as long as they are regularly interacting with speakers of those
languages.
I don't think any app or software can really provide that interaction. Kids don't learn a language like adults try to do it, with learning vocabulary and grammatical structures. There are kids who can learn a language that way, but they are highly gifted, and if your kid does not belong to that 2% of population, showing pictures with assigned words will not have the results you hope for. Actually interacting in Spanish with your kid will be much more effective, in less time spent on "learning".
My wife speaks Catalan with our 3-years old in everyday life, there are some words he only knows in Catalan. When I grew up, I only knew "pollo" and "basura" before learning the German words for it (I'm a German native speaker) because my mom talked Spanish with us kids quite regularly. It works, but it requires direct interaction with the kids. Even a simple memory game helps, but only if someone plays it with the kid and uses the names in the foreign language. 10 minutes of playing memory is better than the kid watching the cards floating by one by one while being told what the animal/thing is called for an hour.
