What is a good App for OSX that locks your Macbook when outside "known" wifi area
You can use ControlPlane where you can set up rules based on various criteria.


  ControlPlane supports multiple contexts where a context is defined as a location or activity you are performing.  Using evidence sources you can create a set of rules that tell ControlPlane what context to apply to your environment.  When ControlPlane enters or leaves a context a set of Actions are performed.