data mining is also of great interest to companies; Google, for instance, uses anonymized GPS data from smartphone users
to map real-time traffic.
External sensors. Early efforts in mobile phone sensing began before the onset of the smartphone age, when feature phones
were augmented with external sensing hardware [96]. Now that smartphones are packed with built-in sensors, external
hardware is, once again, employed to augment the capabilities of today’s phones.
SensorCon’s Sensordrone [97] offers various sensors, including a professional grade fuel cell gas sensor pre-calibrated
for carbon monoxide that can also be used to measure other gases (including, for instance, ethanol, for breathalizer
applications); it also offers an interface to connect other sensors, such as electrocardiography (EKG), water pH, dissolved
oxygen, and CO2. Other examples include iBGStar’s glucose meter [98], based on Cornell University’s Smartphone Cholesterol
Application for Rapid Diagnostics (smartCARD) [99], and InterSoft Eurasia’s DO–RA (DOsimeter and RAdiometer) [100] that
measures the exposure to ionizing radiation.