There does not seem to be any granularity in the services granted to paired bluetooth devices. Once paired and trusted the remote party has full access to all the services on the N900. Don't pair with any devices you don't want to grant full access to the device. This, of course, does nothing to counter the fact that from a trusted device your audio could be hijacked and all of your contacts/calendar events read via Nokia PC/Ovi Suite. Don't pair with untrusted devices.