Capitalize your I’s.
Every time you use the word I, as in the singular first person subject pronoun, the word needs to be capitalized. If you’re contracting the word I with am, have, had, would, etc., I still needs to be capital.
It should also be noted that proper nouns, including the names of products, are usually capitalized. I said usually because Apple makes several products whose names begin with the lower-case i.
When writing the name of your Apple product, even though it is the name of a product (proper noun), and even though the name contains the pronoun I, you are allowed, on these isolated instances, to use a lower-case i.
Example: I’m listening to my iPod.