ControlPlane, a fork of MarcoPolo, brings context-senstive awareness to OS X. With ControlPlane you can intelligently reconfigure your Mac or perform any number of actions based on input from a wide array of evidence sources including but not limited to available WiFi networks, connected monitors, connected and nearby bluetooth devices, currently running apps and other configurable sources. You will find a full feature list at http://controlplane.dustinrue.com/feature-list.
Using fuzzy logic, ControlPlane decides where you are and what you are doing (called a Context) using rules that you configure to then carry out any number of configured actions
An example of how to use ControlPlane may include disabling the screensaver password while at work but enabling it when away from work. Another example would be to set your Adium status and lock your screen if your cell phone out of bluetooth range.
You can download the most recent version of ControlPlane from http://www.macupdate.com/app/mac/39644/controlplane. Once installed you will be automatically notified of any new updates the become available.
ControlPlane is free, open source software hosted at https://github.com/dustinrue/ControlPlane. If you wish to build ControlPlane yourself you can do so by cloning the ControlPlane code to your computer. If you don't have git installed you will need to install either the GitHub client for Mac at http://mac.github.com/ which install a GUI client as well as the command line client or if you simply want the command line client installed you can get it from http://git-scm.com/download. If you need additional help with using Git GitHub is a great resource. You will find GitHub's documentation at http://help.github.com/.
Once cloned, open the project file in Xcode and issue command+b to build the app or command+r to build and run it.