There are one simple way to detect if phone supports WLAN. This is useful if your application only runs in a WLAN enabled phone:
A) Does the S60 3rd device have WLAN chip?
In /epoc32/include/featurediscovery.h file , the wlan key can be used to query for the feature.
Device supports WLAN protocol.
const TInt KFeatureIdProtocolWlan = 109;
B) and how to read the MAC address in S60 3rd edition devices: