Starting today, guests who purchase MaxPass (or have it included with their Annual Pass) will be able to make FASTPASS selections for both Fantasmic! at Disneyland Park and World of Color at Disney California Adventure on their smartphone.
Disney MaxPass is a paid service that allows guests to make FASTPASS reservations for attractions using the Disneyland app without having to crisscross the Parks. MaxPass also includes unlimited PhotoPass digital downloads for the day.
The current price is $15 per person per day. MaxPass is included with Premier and Signature Plus Annual Passes, and can be added to other Annual Passes for $100 per year.
In order to use MaxPass each day, guests must have entered at least one of the theme parks. Once activated, guests can choose attractions, and now entertainment, from either theme park.
Source: Disney Parks Blog