airplay and wireless headphones I'm trying to find some headsets that will work with airplay from either my mac or an iPhone. 

Should i presume all wireless or bluetooth headsets do? 

best, Dan.
Not at all - you should presume the opposite - that all wireless and bluetooth headsets will not work with AirPlay on a Mac or iOS device.

AirPlay requires an Apple certified device (you can't just have any old software become an AirPlay destination) and AirPlay goes over a TCP/IP network and generally uses broadcast packets so it won't find speakers on a different subnetwork without advanced network tunneling and setup (generally sender and receiver are on the same router).

Even though WiFi does share some of the radio frequencies that are the same as Bluetooth - the two do not communicate with each other. At the moment, bluetooth audio connection is much better for stereo headsets as it allows the device to play / pause / control volume as well as sending the music using less battery power than WiFi chipset (to get AirPlay wirelessly) can.

I would expect things like larger speaker systems, receivers and electronics that plug in to the wall (or at least non-wearable battery power) to get AirPlay and light headsets to remain Bluetooth only due to power, size and features.