I want to have raw accelerometer data to use it for sleep study , does fit bands like ( jawbone ,fitbit ) allow to download raw accelerometer data ? or is there are other options ?
If you really want raw accelerometer data you probably want to have the ability to customize data collection, and you are going to end up with DIY logger. Here's an intermediate level tutorial from Instructables that may be useful: http://www.instructables.com/id/ACCELEROMETER-LOGGER-MAKE-USE/
Neither Jawbone nor Fitbit store accelerometer readings, but you can get it from a Hexoskin, if taping a smartphone (running a generic accelerometer logging app) to your study participants isn't an option
Like the app: Science journal. Lying the phone on the bed might work, just like the SleepasAndroid and Sleepbot apps are doing it. However, I understand if you prefer a wearable.