It's not obvious to choose the persistent storage system for mobile apps.
Phonegap provide two ways:
http://docs.phonegap.com/en/1.9.0/cordova_storage_storage.md.html#Storage
local storage (dom storage) http://dev.w3.org/html5/webstorage/
local SQL database http://dev.w3.org/html5/webdatabase/
The main problem here is that the SQL database spec is deprecated and not maintained, also is only available for Android and iPhone