The US House and Senate is widening investigations into mobile location tracking, despite a federal mandate on the books since 2001 that requires wireless carriers to track the location of users.

A report by Reuters noted that the the House Energy and Commerce Committee has sent letters to Apple, Google, HP, Microsoft, Nokia and RIM requesting more information about how devices use and store location data.

The US Senate is also addressing privacy concerns, similarly tipped off by a report that Apple's iOS 4.x devices maintain an internal database cache of generalized location data that appears to never go away, and is compiled regardless of whether Location Services is turned on or not.

The issue has stoked the strongest bipartisan cooperation in American politics seen in recent history, and appears to be generating more interest and scrutiny by elected officials than Net Neutrality, the BP oil spill, employment or the economy at large.

However, the US Congress originally passed the 1996 Telecommunications Act, under which the Federal Communications Commission mandated that, as a report by Geek.com from 2001 noted, all wireless devices "be able to locate 67 percent of callers to 911 within 50 meters that elect the handset solution while those using network technology must be able to locate the caller within 100 meters," a rule that expanded to cover all new cell phones by late 2002.

The purpose of the tracking law was to enable 911 operators to locate mobile users in an emergency. Enhanced 911 services (E911) require mobile operators to relay an emergency caller's location within 50 to 300 meters. E911 laws also apply to many VoIP and femtocell products, such as AT&T's 3G MicroCell, and complicated the deployment of that device due to requirements that callers' locations must be trackable for emergency response purposes.

What has changed in the last decade is that cell phones have shifted from being simple phone devices to being full fledged computers. When Apple's iPhone debuted in 2007, most smartphones ran JavaVM, which limited the capabilities of third party apps.

After Apple added user-accessible GPS services to the iPhone 3G and opened its App Store, it tightly restricted how third party apps could access Location Services, forcing them to ask the user for permission to access location information.

Google's Android OS enhanced the existing Java phone market among vendors such as Motorola, LG and Samsung to run apps of similar sophistication as Apple's iOS, but it also takes a more permissive approach to users' privacy, asking users to grant apps broad rights to access hardware features at their installation.

Both Apple and Google have since expanded their use of location data to power location-based advertising, with both creating opt-out routes for users who do not wish to have their location data used for such purposes. Apple also uses location data to enable users to remotely locate, lock or wipe data from their devices using MobileMe.

Apple has been the target of particular scrutiny for using a database that caches location data to rapidly calculate the user's current location. While this data remains on the phone and is backed up to iTunes, press reports have portrayed it as being instantly delivered to Apple to maintain up to the minute reports of the exact location of the company's 189 million iOS devices.