I would have three switches to turn outdoor lights in my home. The three switches are in different locations (garage, hall, family room). I would like to know if there is any X-10 or other technology whereby all three switches can turn on/off using one switch.

thanks

Yes, you can replce each one of those switch with X-10 active switch. That allows you to either opeate locally or remotely with x-10 signals.

You can either set them up to all work on the same code or you can use a small controller that will broadcast an ALL signal.

Look around at www.smarthome.com

They have a large selection.