More than one bluetooth device

Well, I don't know anything about Bluetooth, but the iPhone only supports a headset profile for voice, so I'd say no just by design.

But, like I said, I know nothing of Bluetooth, so...

The iPhone only supports the Hands-free and Headset profiles(as far as I know). You can't, for instance, transfer files or stream audio with the iPhone through Bluetooth.

So, if you're wanting to use a headset for phone calls while synced up with your car, I wouldn't see why not. That seems obviously practical, but, again, I don't really know.

Hopefully, someone can better answer this for you. Sorry...

One can pair multiple bluetooth devices (headsets, car bluetooth, etc). However by the nature of bluetooth, only one device can be active at a time. So if a couple of devices that have been paired are both on and you come in range of them, first one get gets the connection.

I have a TomTom 510 Go in my truck I use for Hands Free as well as my Plantronics Headset that is BT also. They are both on and paired with my iPhone.

When I am in the truck and have my TomTom and BT Headset on and a call comes in, I get a notification screen showing the incoming call and listing the devices that I can choose from to answer the call with, or, if I hit the talk button on my BT headset, it uses that, or if I use the answer button on my TomTom, it uses that.

Many ways to use more than one BT Hands Free device, just have to know how the phone will act when more than one is "on".