Here’s an interesting article that shows the need for apps to work when they are not connected to the internet: http://www.tuaw.com/2011/05/10/15-of-mobile-apps-launched-while-offline/. This shows the need for apps like Packrat exists, although Packrat is on the Mac, so it solves the case for laptops.
What about iPhone and iPad? Are there enough Backpack clients for the iPhone and iPad? Do they have an offline mode? Would you like to see Packrat for the iPhone or iPad?