[html5] Creating Offline Web App

[Smylers]

Hi. We want to create a web app that can collect data on a tablet
without a network connection, then upload to the server later. Which
technology should we use for the ‘works offline’ part?

I see app cache is now being dropped, and using it is “highly
discouraged” by MDN:
https://developer.mozilla.org/en-US/docs/Web/HTML/Using_the_application_cache

MDN recommends service workers instead, but I see they aren't
implemented in WebKit yet, meaning our web app wouldn't work on IPads:
https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API/Using_Service_Workers#Browser_compatibility

Looking back at app cache, it appears to be supported in all browsers
(though now warns in Firefox).

For an app we're writing right now, technology that's already widely
implemented in browsers sounds superior (whatever its inherent limits
and flaws) to one that may be technical better but doesn't work on one
of the most common brands of tablets. But obviously that MDN advice is
there for a reason, and I don't want to arrogantly dismiss it without
understanding the situation better.

Any wisdom on what we should choose gratefully received.

Thanks.

Smylers
-- 
http://twitter.com/Smylers2