GPS units were the hottest selling item last Christmas. Australia has finally embraced the benefits of a gadget that tells you where to go with a few extra bits and pieces thrown in.

Three states of Australia are running a trial to use the technology that powers GPS, to ensure our cars maintain the speed limit ceiling and save lives through less crashes from speed.

GPS was created by the United States Department of Defense to provide accurate positioning of military vehicles. It was made available for commercial, non military use in the early 1980s. Technology has allowed prices of SatNav receivers to drop and today we can now afford to have one in our cars.

The plan, is to use the positioning and speed monitoring benefits of GPS to monitor your speed and slow the car if you exceed it. We discussed some concerns on the Today Show this morning, however we didn't get time to address a pretty major one. GPS requires line of sight to at least four satellites, if you are driving in a built up area with high rise buildings your GPS may lose line of sight. Should this happen, your system will not know what street your car is on and must estimate its position. I've had this happen to me already when driving in the Sydney CBD and it is so annoying, the SatNav has a major melt down and is practically useless. I can handle that for driving from point A to point B, however if the streets I am driving through have different posted speed limits what will that do to my safety and that of others?

We're planning to test this technology out on CyberShack TV next week, to air in July. I will let you know what limitations we find in our review.