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?
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.
To my knowledge, there aren't any AirPlay-enabled headphones at the moment, nor have any been announced. I wouldn't count on any ever coming out to be honest.
Wifi is simply more power hungry than Bluetooth, which makes it ill suited for a situation where you want the device to be as light as possible.
I think you are a bit confused about what AirPlay actually is. While in iOS both AirPlay speakers, as any Bluetooth headsets can be accessed by the same "remote speaker" button, the two technologies are very different.
AirPlay requires a local wireless or wired network. It transmits an uncompressed audio stream (as opposed to Bluetooth), and given it works across an entire local network, it isn't restricted in distance as Bluetooth is. AirPlay discovery happens automatically across the entire network with Bonjour, while Bluetooth devices need to be paired. Given the power requirements of a (wifi) network adapter, and probably because of licensing costs as well, you will not likely see AirPlay in a wireless headset any time soon.
However, I'm under te impression you are just interested in knowing which Bluetooth headsets are supported by iOS/Mac OS X.
For iOS, you can consult the following link on which Bluetooth profiles are supported on which iOS devices. You can probably find matching information for the Bluetooth headphone models too.
For Mac, you should be able to pair the Bluetooth headset just fine, but it is unlikely iTunes will work nice with that in a way you can expect from actual AirPlay devices. You'll probably need to change your primary audio output in System Preferences to have all audio output directed to the headphone.