I have a Sony Ericsson Satio which when trying to connect produces a message on the iPhone 4S saying the other device is not Bluetooth 4.0 and so it is not allowed to connect.
You cannot connect to another phone via Bluetooth. This has never been possible with any iPhone. Don't know about the Zenec. Perhaps it needs an update of some sort. Have you checked with Zenec?
Bluetooth is indeed open, but there are a number of profiles and few if any devices support them all. The ones that Apple has up until iOS 5, at least, supported can be found here:
It's a little bit worrying Apple hasn't updated that list for iOS5 but looking at the link (thanks for that, very helpful) it appears that Apple have tightened up their rules in iOS5, the new Bluetooth system or their is a geniune fault in the software.
Also, this being my first iPhone I am kinda shocked the device cannot connect with other phones. Why would they not allow that? I understand you may not know that particular answer, more asking myself.