Well, I think that phones are most likely the most likely exposure point to hacking attempts - they are ripe for exploitation and theft of personal data.
If I am not mistaken, there have been cases where police were able to do a warrantless search of people's phone data, REQUIRING the phone owner to give them access, simply because the courts looked at a fingerprint ID mechanism on a phone differently than a more traditional password.
But again, the real exposure is that your phone is exposed by potential flaws in ever-rapidly changing OS code for phones, as well as exposed because of web site flaws that allow things like Clear Case Intercepts to happen, AND, when you connect your phone through a public network, you have an even more insidious exposure.
I would urge you to rethink the notion of keeping passwords stored on your phone. When I have some site I sign up for, where I need a user name and password, and I don't access that site frequently, I will often send an email to myself, with a subject line saying something like: Billy Bob's Crab Shack and Auto Detailing site account info, and then in the body of the email, I will add text that will clue me in to the user ID I used, and I will also add a password hint sentence that gives me and only me enough info to where I will understand what I used for a password. So, even if my email gets hacked, nobody would be able to figure out any of my user ID's and passwords for any of the sites I have set up accounts on.
Best of it all for you - stay secure,
Bob Bone