updated 10:30 pm EDT, Wed September 8, 2010
iOS 4.1 comes with field test and GC-ready games
Following today's launch of iOS 4.1, discoveries have been made both in the firmware itself and for new updates in the App Store. The update is now known to have restored the Field Test Mode that had been pulled in all versions of 4.0. Dialing *3001#12345#* and tapping Call will bring up a signal measurement in dB, with higher numbers typically better; hitting the home button returns to normal.
The test may help those looking to quantify their signal results beyond just the simple five-bar system on the phone itself. Speculation had surfaced that the mode disappeared to avoid providing support to the "death grip" issue, though that's now unlikely to be true.
Separately, Apple has compiled (App Store link) the list of games that work or will work with the achievement, multiplayer and score systems in Game Center. Among the highlights are Pangea's Cro-Mag Rally, Enigmo 2 and Nanosaur 2. Well-known games such as Angry Birds, Carcassonne, Flight Control, the Pac-Man games and Zen Bound 2 have also made the leap. Only a handful, such as Cro-Mag and GraalOnline Classic, officially support multiplayer play through Game Center's friend system.
Game Center acts as an effective equivalent to Xbox Live for iOS by creating a common platform for online friends to join and start multiplayer games as well as compare achievements and scores.