Is it Your Iphone? If it is there seems to be nothing wrong with that. A person wants to know what is going on with his stuff.
If it is someone else’s Iphone then I wouldn’t recommend it because it is an invasion of privacy (which would also be a torah issur due to the fact that you follow the laws of the country you live in)
And waht you are talking about is a takana Rabanu Gershon to not go through other people’s mail. (used to be letters then but would apply to E-mail)