Given that you're actually needing offline availability, the easiest way (as long as you've already got a mobile-friendly design) would probably be to deploy sp

Given that you're actually needing offline availability, the easiest way (as long as you've already got a mobile-friendly design) would probably be to deploy special wrappers for your DAOs (API classes, whatever), that perform the necessary caching to allow for it. PhoneGap seems only interesting if you wish to commit the cached changes (or is offline = read-only?) upon regaining of connectivity.