welcome to AF!!!!!!!!!!!!
to be honest, if someone wanted to hack your phone, it can be done no matter what you do. i do mobile banking from time to time, but most is done at home. And most mobile banking apps are fairly secure and encrypted. I'm not that paranoid enough to go to great lengths to hide my identity. For me i always monitor my account and Wellsfargo has been great. I have only had one unknown weird activity which i notified Wells Fargo and they refunded my money. They locked my account, gave me a new account and card just in case.
what i'm trying to say is just use your common sense. don't do mobile banking where there are a lot of people around, especially if you are at a Starbucks or other public place. Also monitor your account and you should be fine.
you can install, one of many anti-virus protection apps that are out there. I have been using Lookout, since the early days of Android. but there are many others like Avast and Norton.