This post replies very well to the question \"How to get Advertising ID in android?\"...
but not how to use it.
I would like to know
If anyone is looking for this answer the parameter is &adid for android (&idfa for iOS). You also apparently have to send the store ID in the &aiid field (ex : com.android.vending for google play) and the app ID in the &aid field.
So basically in an android app hit you have &adid=abcde-fghij-klmno-pqrst-uvwxy&aiid=com.android.vending&aid=com.yourapp.android
Still testing to get the demographic report working with server side requests.