On your Mac, go to the Bluetooth preferences panel after pairing your Nexus to the Mac.
Select the Nexus in the left-hand menu, then use the little cog to pull down a list of options. Select "Edit serial ports..."
Click the little '+' icon, and in the Port Settings section, select OBEX Object Push. Protocol should be automatically set to RS-232. Click "apply" (and probably "require pairing" to be nice n secure) et voila!!
You should now be able to, say, go into your gallery and send a file from your N1.