I am seeing more and more online/offline apps on the web - Google, when can we have "work offline" in our Gmail?

If IScrybe and Salesforce and Zimbra can do it, surely Google can build Gmail so that you can just work offline on the laptop when you’re away and then click either “sync” or “work online” once you’re back on the net. I hope that we can expect to see the same thing with Google Docs & Spreadsheets, perhaps if it was crossed with OmniDrive so that where ever you wrote your docs, they were stored everywhere, on the web, and in your hard drive.