Satchel for iPhone puts your Backpack account in your pocket. True, you could access Backpack on Safari, but it is hardly optimized for the tiny screen. Satchel provides a much more elegant interface to your pages, lists, notes, reminders, and—with a paying Backpack account—calendars.
I’m terribly impressed with the developer right now. I’m testing the free Satchel View before I buy it and things are looking pretty great now that I’ve gotten connected. I made an offhand comment on Twitter about my difficulties using my OpenID to log in. Wholly unexpected I got several replies from the developer about what was going on and how to fix it (it doesn’t play nice with OpenID delegates). That’s above and beyond what I had expected.