Use Only Mic in Bluetooth Headset, While Outputing Audio to 3.5mm Jack? Is it possible to use only the microphone in a Bluetooth headset, while letting my Android phone sound through amplified speakers connected via the 3.5mm jack?

More specifically, I am looking to use my Nexus One that way. I have already solved the speakers via 3.5mm jack problem (thanks to @Adrian). I am now trying to see whether I can connect a standard Bluetooth headset and use its microphone.

It's OK if the same audio comes through the earpiece in the Bluetooth headset (i.e. it doesn't have to be disabled). I just want to make sure that if I buy &amp; connect a Bluetooth headset, it will not disable the 3.5mm jack.

Is this doable? Do I need to change something in the setting? (I do have CyanogenMod installed, if this helps).
The term "Bluetooth headset" is very broad. Different headsets support different Bluetooth profiles.

The most common profile is HSP (used mainly for phone calls), which seems to be independent of the headphones jack you are referring to. So pairing your Android device with a cheap headset that supports HSP only (e.g. Plantronics 242) won't affect audio routing to the headphones jack at all. Your Bluetooth headset and your Android device will continue to operate in parallel, but each handling a different audio stream (channel).

If you are looking to disable the microphone only in your Android phone, it seems that only a headset with an A2DP profile could be a possible solution. You may want to read at the following thread: How do I send Bluetooth audio from the Stereo (A2DP) to Headset (HSP) profile?