To accompany the recent Xbox 360 dashboard update, 1337pwn.com released a new version of their Xbox Live friends-management iPhone application. iNXES lets you view your friends list in the NXE form complete with avatars, gamer scores, and online status.
In my testing (on 3G and WiFi), performance was pretty poor. Scrolling through categories or through my friends list was sluggish, and some of my friends' avatars have been updated on Xbox Live but are not showing on iNXES. I was, however, able to see profile data, achievements, and game history.
Unfortunately iNXES (like the previous version) still doesn't support automatic friends list syncing, so you either have to enter all of your gamertags by hand, or use a convoluted import utility (which obviously doesn't keep your list updated if you make changes). Despite the annoyance, the utility did import all of my friends successfully.
iNXES requires the 2.2 firmware, and is free for download in the App Store.