It's not a free app, but it should work how you want it to and does not require root. I also use it with Astrid for location based reminders. For example, I set up Costco in Locale and created a list called Costco in Astrid. Whenever I arrive at Costco it reminds me of the things in my list. Very similar to Siri in that respect, but it does a lot more too.
If you set up your Default to WiFi "off" and set up your Home to WiFi "on" it will do what you want. Anything above Default will override default settings.