The wife wanted to know when people or cars come in the driveway and some research provided me with a few ideas. These products seemed the most sensible and suited to the endeavor:

http://www.autobarn.net/designtech-30078.html 

http://www.autobarn.net/dakota-alert-dakwma-3000.html 

   While at Radio Shack I found a wireless motion sensor that can be used to monitor your driveway, doors, or other places for people or cars passing by. Called "The Reported wireless alert & security system", its an infra-red proximity detector meant for outdoor use that communicates with a small base station wirelessly.

   I assembled the few parts making up the sensor in about 10 mins, mounted it on a tree at the mouth of my driveway about 3ft off the ground, tested it by waking by the sensor several times and overall find it to be a decent little device. I can even add up to 3 more sensors to the base station to monitor additional locations.

   All in all a good buy.