You may want a Context based on the State "Wifi Near". I think you'd enter your SSID or router MAC and click the "Invert" checkbox. Theoretically, this would trigger when wifi is enabled and it no longer sees your router. The task, of course, would be to set Wifi to off.
If that doesn't work, another option would be to trigger wifi based on geographic location. Turn it on when you get near your home, turn it off when you leave.
I am kind of curious how this would react when you try to access a wifi network away from home though.
Yet another option would be to turn on wifi when you open specific apps (browser) in your home area, and then shut off wifi when you break either of those 2 conditions. Then it's only running when you're using it.
A few of my profiles:
- plug in headset: pull up menu of audio apps
- camera on: turn up screen brightness, turn it back down on close.
- day and night notification profiles. turn off all radios except phone during "sleeping" hours when at home. Adjust screen and audio.
- turn on gps when using navigation apps
- increase screen time-out when ebook apps are open.
- Phonefinder (I think I saw this this on lifehacker): If phone is lost, I SMS "SOS" to it from my son's phone. It then grabs the GPS coordinates and SMSs them back to my son's phone. I was actually thinking I'd create a couple different SMS commands for it to complete in various scenarios (ie: scream bloody murder if I track it to a public place but it's out of view, take periodic photos and email them to me, set an SMS trigger to electrocute the person holding my phone

). So far, the only other phonefinder profile I've built is to play a siren sound when I lose it around the house, which I do sometimes (usually in the garage or next to my bed).
Tasker is pretty damn cool. I'd love something like this for my laptop.