I currently have WLAN enabled all the time for triangulation, even when I'm not near an access point I can use. Is there any way to automatically enable it whenever an app requests location information, like it is done with the GPS?
As far as I know this is not possible. IMHO, it contradicts Google's incentive to have an as best as possible geolocation service.
Some background information:
There is now a feature that turns on WiFi for location purposes. Settings->Wi-Fi->Advanced->"Scanning always available"
You can turn WiFi off to save power, but still have location requests turn WiFi on temporarily.