This sounds pretty normal to me. Note, I do not equate "normal" with "acceptable". One of our roles as parents is to create consequences for the normal but unacceptable behaviors that children display.
It sounds as if you are worried that her behavior is getting worse. That is a possibility, and in any case, dealing with her when she has become a rebellious, hormonal teenager will be even more challenging. What you want to do is start developing ways to correct her behavior (or, even better, to teach her to correct herself) now when she is young.
I'm a big fan of crafting consequences to fit the "crime". She broke her iPad in a fit of rage. Et voila. She has created her own consequences. You can sympathize with her ("I'm sorry you broke your iPad and that you don't have it any more, I know you liked it a lot..")
But in order to get her iPad back, you certainly need a way to be certain she won't do it again. ("It costs too much to buy expensive electronics if people are going to break them" "I'm not, I promise", etc, "Okay, I'd really like for that to happen. How can I help you learn how to express your anger safely? How about this..? Do you think that's a good way to let yourself be angry?") Show her that you are applying those techniques yourself, when you are angry, and be prepared to react calmly and appropriately when she brings it to your attention when you fail. She'll be far more likely to imitate you than to simply do as she is told.
Do you read to her? Maybe you could read a couple of books to her about dealing with anger, and then afterwards discuss together how she might apply what she has learned to both the original incident and to other things that are currently making her angry in her life, or things that might make her angry. Maybe at the dinner table you could each talk about a time that you were angry during the day, and whether you were able to apply your safe anger habits. If you failed, tell a story about what it would have been like if you had handled the situation that way you wanted to.
This will help to teach her to "own" her own anger, and make you a partner in helping her to cope with her own problems. Make sure she understands that it is okay to be angry, just not to do hurtful or destructive things while she is being angry.
Here are a few suggestion for good childrens' books that deal with anger:
When Sophie Gets Angry, Really, Really Angry by Molly Bang
Alexander and the Terrible, Horrible, No Good, Very Bad Day by Judith Viorst
When I Feel Angry by Albert Whitman
I'm Mad by Elizabeth Crary (also I'm Furious by the same author)
I'm Not Bad, I'm just Mad by Anna Greenwald
Once you have reached an agreement on how she wants to handle her anger, you might consider telling her that before you can buy another iPad (or any other electronics device that might be seen as a substitute) she has to show you that she can use her "good anger habits" for a period of time, say, two months.
When she has a fit of anger and forgets to apply the solutions that you and she discussed before, don't yell at her, just firmly and calmly bring it up "Let's see, we talked about ways to express your anger. Which one is this? Are you counting to fifteen with your eyes closed? Have you taken ten deep breaths?" Then give her a chance to do things "the right way", and if she does, you move on as if she'd done it right the first time. Praise her for making the effort. Only if she adamantly refuses to make the effort should you "reset the clock" and tell her, regretfully, "Oh no, I'm so sad that you weren't able to apply your good anger habits. I'd like to give you another chance, shall we try again?"
Don't set the bar so high that she can't reach it, but don't lower your expectations too low, and once you make an agreement, stick to it.
One final thing: educate yourself about how to handle your childrens' anger. Here are a couple of good articles:
http://www.huffingtonpost.com/dr-gail-gross/dos-and-donts-of-teaching-your-child-to-cope-with-anger_b_3202744.html
http://www.parents.com/toddlers-preschoolers/discipline/anger-management/helping-kids-handle-anger/