I find the best thing to do is look for the apps that are totally offline that way you wont get charged anything whilst using them.
ones like Orlando attractions, give info on the rides, requirements, if they have fast passes etc.
iOrlando is good as well. It is a map of the orlando area with all points of interest for I drive, Lake buena Vista, Disney area as well. It also has Seaworld, busch gardens and aquatica maps with them
Walt Disney World complete travel guide has maps, in depth info about the restaurants with prices, what kind of food they serve must do's etc
They are all offline and can be used without costing anything
The problem with any of the wait time apps is that they need to connect to the internet, which if i remember is £4 for every 1mb of information which is extortionately expensive. 1mb may not sound a big amount but you will use an awful lot just using the internet even for a few minutes.
So the best thing to do is just check the wait time boards or do what us english do best and just queue lol
And finally make sure you turn data roaming off in general>network>data roaming or you will have a very high phone bill when you return home!