Developers are getting a preview version of iPhone 4′s sdk today, Steve told us at the Apple announcement. New features can be implemented in their apps and ready to go when the OS is officially released this summer.

The new sdk s include a framework for hardware accelerated math functions, In-App SMS, embedded PDF metadata, Photo Library access, Calendar access, iPod remote control accessories, regular expression matching, address data detectors, performance profiling tools, automated testing, draggable map annotaions, image I/O, carrier data information and full access to still and video camera data.

These will give the end user 100 new features, including create playlists, Bluetooth keyboards, rotate photos, Persistent WiFi, sync IMAP notes, wake on wireless, places in Photos, spell check, home screen wallpaper, etc.