Sometime in the next few weeks, Google will be rolling out mobile editing capabilities for its Docs & Spreadsheets applications. When I say mobile editing, I mean it is only for the iPad and Android at this time. We'll see about the Blackberry and other smartphones.
There are already third party apps you can use now for mobile editing, including Office2 HD, Quickoffice and DataViz (recently purchased by Research in Motion, parent company of Blackberry).
In the same announcement on Monday, Google also unveiled a new two step process for user authentication on mobile devices. The one-two login proces will be optional requiring users to not only use a login, but a second randomly generated password sent to their phone each time.