vaistech is a vendor here on clublexus, you can pm them.
you can also email firstname.lastname@example.org
. eugene is very nice and friendly and he can answer any of your question. i haven't sold a sl3b so far (my clients have gone either sl3i or ivic) but i remember from talking to eugene that the unit does have usb port
you can also see from their installation manual (page 4)
and it shows the usb port specifically listed for charging only
so it looks like you can hide the unit, run an usb extension to center console or any place of your preference charge your phone, and connect through BT