Overview:
Google Checkin is the service responsible for “checking in” to google with data in /data/system/dropbox. Crash dumps, lastkmesg, dmesg, full logcat dumps are in here. On google checkin (open up market, sync gmail, login to a google service) this data is synced.

How it works:
App Responsible:
 /system/app/GoogleServicesFramework.apk

Data is written to:
/data/system/dropbox

Data is sent to:
https://android.clients.google.com/checkin