Bluetooth Device (disappeared) the greyed out one.
iphone 6: 8.02
imac 27, Yosemite, 10.10 - preview 8
I couldn't remove a bluetooth device as most couldn't - it was greyed out and you could not "forget the device".
Fix was simple, for now, do NOT login from the same iCloud account on both devices.
Login from a DIFFERENT iCloud account on the Mac. Do not change the iPhone iCloud account.
Once you have two different iCloud accounts (one on the MAC one on the iPhone), and the bluetooth device (listed as the mac on the iphone) magically disappears from the iPhone list. Something in the bluetooth device list WAS tied to that iCloud account -
It still won't pair, but at least is not listed on my bluetooth list on the iphone anymore.
So to test: Logged back in to the same icloud account as on my iphone from the Mac. The bluetooth device is still not there on the iPhone.
Summary, back to the same iCloud account on both the iPhone and Mac. Bluetooth device that would not forget is now gone.
Update: 30 minutes later, it appeared back on the iPhone - again, with the same iCloud account signed in on both the iPHone and MAC. Until Yosemite goes prod, I'll simply sign with different accounts to keep my iPhone clean.