Apple's new iPhone 6s and 6s Plus have a new M9 co-processor that serves as a distribution center for all the digital information coming from the phones' various sensors, including the gyro. The iPhone 6s uses the same InvenSense 6-axis gyroscope and Bosch Sensortec 3-axis accelerometer that were working fine in the previous iPhone edition, but here they are presenting a problem, at least with some third-party augmented reality apps.
Users have been reporting that while trying to watch the night sky, they used an AR app called Sky Guide that lays over stars and constellations names and positions. On the iPhone 6s, however, this map sort of floats all over the place, indicating bad communication between the input from the gyro/accelerometer, and the app's code.
Apple's default software, like Maps, doesn't experience this, while other third-party AR app makers complained that they have the same issues reported only on the new iPhone 6s, so it's a matter of buggy APIs, which hopefully will be fixed by Apple soon. In the meantime, don't shake your iPhone 6s uncontrollably when an AR app is all over the place, the problem is likely software-related. Here's the statement from the makers of Sky Guide: