Joe and Aaron,
This chapter was well done.
A few hardware items of interest are worth noting here as well:
- iPhone 4 and iTouch 4th generation have gyroscopes built into the device.
- iPad, iPhone 4 and iTouch 4th gen. all have 12-bit resolution for their accelerometer data. Legacy devices have an 8-bit resolution. Something to consider if your filters are causing issues on older devices.
Session 423 talks about Device Motion which everyone should start transitioning to for the iOS4 platform. You can still use this new API to get to Accelerometer data on older devices.
Here is the URL but you must be a registered iPhone developer to access this link: https://developer.apple.com/videos/wwdc/2010/