Can I use my iMac's mic and speakers for a call with my android 2.2 phone (through Bluetooth)? I'd like to use my iMac's audio (i.e., microphone and speakers) for a call that is handled on my Samsung galaxy i5000 Android 2.2 phone. Is that possible?

I've paired my iMac (OSX 10.6) and smartphone through Bluetooth.
Then, during a call, I opened the context menu on my phone (where you can also enable/disable the speaker of the phone), but the Bluetooth icon is disabled. (although Bluetooth itself is active and working, e.g. from my iMac I can see the files on my phone).

Is there any way to get the above working?

(I wondered whether to post this under apple- or android-stackexchange, but given the Bluetooth icon being disabled, I decided to post it here)
The reason for the Bluetooth icon being disabled is that you haven't paired the phone with a device that supports the Headset profile. Bluetooth uses profiles to categorize which services a device supports, and Macs don't support acting as a headset, only connecting to a headset (see list of supported profiles).

To use this functionality, you'd need additional software which enables the Mac to act as a headset and connect to a headset gateway (which your phone most likely supports).