Within the next month or two, the Go Tucson app will allow you to pay parking tickets from your smartphone. The app from Park Tucson already lets you pay at parking meters and can be used for fares for Sun Tran buses and the Sun Link streetcar.
Aside from making it easier to pay a fine, the hope is that the new feature increases payment compliance. For people who don't want to use a phone, the City recently launched a new online ticket payment portal (link below). Payments still can be made over the phone, in person, or via mail.