So from what I understand if you do not jailbreak then your phone is reasonable safe but:
This is what hackers/criminals like. They want to encourage jail-breaking because it makes there life easier. So in the same way you might be sent a picture of a beautiful lady and asked to click on a link. iPhone users are loured into opening up their phone to hacks by the increased usability.
I do not know the google wallet thing but seems ridiculously slack.
How much money can be held on an account?
How easy is it to shut down the account if you loose your phone?