Q:

(How) can an operating system be installed purely from a wireless network?

The title really says it. 
I was wondering how if at all, an OS installer (?) can be launched from a wireless network.

A:

I think the challenge here is that most preboot systems dont have much support for wifi.  A lot of them can be configured to be bootable with the driver of your choice, but I have never seen a working PXE wifi adapter.
In this case use a wireless bridge.  In this scenario you configure the bridge to connect to whatever wireless network you want, and then hardwire the host and boot normally as you would with a wired connection.
These are fairly popular for game console devices.  An example is here:
http://www.dlink.com/products/?pid=333
Hope this helps you.  Similar to the comments and mfinni's answer the setup should be no different, the challenge is with the systems support for wifi and not directly on the network itself.

