I wonder if anybody knows what is the easiest way for an application
program to receive notice of certain fairly basic WLAN-related events,
such as when an access point goes out of range, association changes,
connections/disconnections, etc.

Basically the same stuff that you can (or *should* be able to) see
through the iwevent(8) command line tool.

I've found mention of rtnetlink, IFLA_WIRELESS and such things but it
sounds quite complicated.

Linards Ticmanis