The Kelsey Smith Act, which becomes effective on August 1, 2010, will allow any law enforcement agency in the State of Minnesota to simply ask for and obtain from the wireless companies the geographical location of any of their telecommunication devices, (and thereby the location of the person carrying such a device) by simply stating that it is an emergency situation that involves the risk of serious physical harm.
The wireless companies are able to pinpoint with excellent accuracy the location of the devices that are part of their network by the use of their cell phone towers. When the phone is being used, but also when it is not, it communicates with the nearest tower, or the tower with the stronger signal; however, in any event with one tower and one tower alone. Based on the strength of the signal and the location of the tower your location can be easily ascertained. Imagine driving from Rochester to the Twin Cities. As you drive along you phone will send a signal (ping) that will be picked up by a certain tower. As you progress in your trip the ping will be captured by a different tower and so forth. Thus your location and your progress are easily monitored. Do not confuse this with the GPS function that some smart phones have and that can be turned on and off. The pinging is far more basic and is part of every phone, where you are using them, or not, whether they are on or off.
Prior to this law coming into effect the law enforcement agencies had to obtain a subpoena from the Courts to get the ping records of a particular cell phone. This law does away with the need for judicial involvement and simply relies on the law enforcement agencies to simply state that there is an emergency and that the is the possibly of serious harm. Imagine being an abuse victim and not wanting to be found. Your abuser can say you are lost, it's an emergency and that you could be harmed. The police obtain the records of your phone location and presto you are found and reunited with the abuser. And even if the police lets you stay where you are, the abuser can still obtain your whereabouts because the police investigation reports are public data.
As often is the case the question becomes how much do you trust your government and along the same lines quis custodiet ipsos custodes?