2nd gen ipod touch
You need to have at least a 2nd generation Touch to have bluetooth capability...and you need firmware version 3.0 or greater to unlock it. Firmware 3.0 I think is around a $5.00 download.
As far as headsets. I remember reading that with the 2nd generation Touch...bluetooth headset compatibility is limited. The 2nd generation Touch bluetooth ability I think is geared more towards bluetooth speakers & gizmos like that other than wireless headphones.
You of course can use a "wired" headphone or "bud" with a wired microphone.
I also read (I couldn't find the article) that the 2nd generation Touch does have the capability to use bluetooth headsets...just that this ability wasn't unlocked in the firmware 3.0 upgrade. There is some speculation that maybe this ability will be unlocked in a future firmware upgrade.
I think the bottom line is...maybe Apple (at the moment) doesn't want folks turning an iPod Touch into an almost as convenient device to use as an iPhone (using something like Skype for phone calls).
Hope this helps,
- Nick