Apple has released iPhone 3.1 OS beta build to developers. The OS 3.1 SDK is integrated with some new features as

• Faster boot up
• Tethering hack still working
• When you try to move an app, before that iPhone vibrates
• Toggle “Fraud Protection” option in Safari
• Allows to save a copy of edited video instead of replacement
• Voice control works over Bluetooth for 3GS

We already posted iPhone 3.0 OS to download and this is the first beta version of iPhone OS 3.1, so there would be many more features revealed furthermore.