I don't know, maybe I am in the miniroty here, but I don't believe kids should be over exposed to electronics at an early age. Especially owning their own before they are even fully cognitivily developed. (Which according to many sources is 10)
I don't have kids as of yet and when I do, I will still not them own their own or use mine until they are at least 12. Teaching respect and responibility is one thing but letting them use electronics too much or own their own is another. I don't think its right. Give them a book, send them outside, give them Play Dough and Legos, for crying out loud. While I think that electronics are wonderful and amazing, it still inhibits the development of their imaginationand studies show it shortens their attention span greatly.
Wanna teach them responsibility get them a gold fish.