MacRonin recommends a press release over at the EFF on their recent court victory affirming that cell phone location data is protected by the Fourth Amendment. Here is the decision (PDF). "In an unprecedented victory for cell phone privacy, a federal court has affirmed that cell phone location information stored by a mobile phone provider is protected by the Fourth Amendment and that the government must obtain a warrant based on probable cause before seizing such records. EFF has successfully argued before other courts that the government needs a warrant before it can track a cell phones location in real-time. However, this is the first known case where a court has found that the government must also obtain a warrant when obtaining stored records about a cell phones location from the mobile phone provider."