After plugging in the Belkin Mini BluetoothV4.0 USB Adapter to fix my erratic Magic Trackpad problems on my MacBook Pro, there was no obvious way to tell if it was identified or working.
The solution was to download the Bluetooth Explorer app, which is part of the Hardware IO Tools for Xcode bundle. This is only available from the Apple Developer site, which requires free registration to access. I can’t link to the download directly, so you’ll need to search for “Bluetooth” from the Downloads for Apple Developers page. One thing to watch — the results list routinely came up blank when I was poking about on that page. This seems to be a glitch with the site, since it happened to me with both Chrome and Safari. Flushing my browser cookies and cache fixed it.
Open the downloaded file (“hardware_io_tools_for_xcode__october_2013.dmg”) and drag the Bluetooth Explorer app to your Applications folder.
Nothing appears to happen when you run Bluetooth Explorer, but that’s because there’s no window and everything happens via its menu bar. Select HCI Controller Selector (⌘K) from its Tools menu and the Host Control Selector dialog box appears.
The Host Control Selector dialog has a drop-down with, in my case, two options — the default “Apple BRCM” Bluetooth adapter and my new Belkin adaptor with “Broadcom Corp” Bluetooth chip. I just selected the Broadcom option, paired my Magic Trackpad with it in the usual way (System Preferences > Bluetooth) and I was done.
The Host Control Selector dialog states that any changes are not retained after a restart, but mine certainly was and the new Belkin adapter seems to take precedence over built-in Bluetooth.
There’s a bunch of other useful stuff in Bluetooth Explorer for troubleshooting Bluetooth problems, but thankfully, I didn’t need them.