App recommendation

Yesterday, I got an advise from my cousin that i should use smartphone to help my kid feel interested in learning. I'm a tech lover but i don't know for sure if this is good for my kid or not. i don't like the idea to let my kids stick their eyes to smartphone or tablet all day long but i still take it into my consideration.

By chance, i found an app- Buddy learns the colors is now from paid to free while i was trying generate file for my blackberry on choilieng.com($2.45=>Free). i don't know if i should purchase paid apps or install free apps. If you have any idea about this, suggest me some apps. I also want to teach him shapes, sounds, numbers and objects.... is there any app like this?

Thanks.