Apple has today seeded the second beta of iOS 9.2.1 to developers. This comes three weeks after the first release. In this update we see some minor bug fixes and improvements. Other than that we aren’t sure what’s new. Apple usually doesn’t seed such minor updates to developers. However, this one contains things that may affect how some apps function.
Developers can get this update from Settings > General > Software update > iOS 9.2.1. If you don’t have it yet you can download it from the Apple Developer Center.