Thanks for your message and sorry for the slow reply. I am currently working on a two projects that relate to your question.
You are correct that many of the default GGIR argument values are tailored to wrist-worn accelerometer. However, GGIR is designed to be adaptable to any sensor location. There are about half a dozen of publications that have proposed cut-points for hip or waist worn accelerometers to study physical activity, you can use those cut-points in GGIR. So, I think a basic physical activity analysis is already possible.
Less well understood is the value of GGIR's sleep detection for waist-worn accelerometers. If you know of any polysomnography data sets where an accelerometer was worn on the wrist then that would be great. Also, datasets with sleep diary and hip-worn accelerometer could be valuable.
Let me know if you want to chat, and we we can explore how you best contribute.
Dr. Vincent van Hees
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