I have never used jaxx wallet in iphone but AFAIK the wallet data isn't stored in the icloud backup. Since jaxx wallets allows user to have complete control over the keys, storing on a cloud backup server might expose the keys at some point of time. Hence the backup file (not completely sure) would be stored in a encrypted format in the form of .plist file which is quite useless and they would be available in the com.kryptokit.kryptokit app domain folder. I have heard people trying to break the .plist file using a sqlite but didn't come up with favorable outputs.

So, you should write the 12 words in a piece of paper as instructed by OmegaStarScream and store them in a secure place. If you tend to lose this backup phrase, I am very much sure you will have a very bad nightmare of losing all your funds stored in the wallet. Hence, there is only way of having a backup of your funds and i.e through writing up the 12 word phrase.