Question

I would like to use in-app billing in my android application (instead of creation 2 versions of application – free and pro). If user paid, then additional options in Preferences should be available.
My application synchronizes data with website (not my).
Each time synchronization happens, I would like to check if user paid or not.
How should I do it?

Answer 1

I think the easiest means for you would be to use Managed purchase. More on it is at http://developer.android.com/guide/market/billing/billing_admin.html#billing-purchase-type

The “manage by user account” purchase
type is useful if you are selling
items such as game levels or
application features. These items are
not transient and usually need to be
restored whenever a user reinstalls
your application, wipes the data on
their device, or installs your
application on a new device.

Update: website and API updated refer this now https://developer.android.com/google/play/billing/api.html