1) How do accelerometers measure distance?
They do this by integration of acceleration to obtain speed, followed by a further integration to get distance.
2) How accurate are accelerometers in measuring distance?
Accelerometers can be fairly accurate in measuring distances with some studies reporting up to 97.4% accuracy (Conger, Strath & Bassett Jr,2004). There are, however certain speeds that each model of accelerometers work best. For instance, FitSense accelerometers were found to be most accurate when measuring walking speed of ≤6.4km/h and running speed of ≥9.36km/hr(Conger, Strath & Bassett Jr,2004). Nike Plus, on the other hand, accurately measured distance for speed ≥82m/min (Kane et al.,2010)
3) What other technologies may measure the parameters as given by accelerometers?
GPS is another technology that would be able to measure speed and distance.
4) What are the benefits of using accelerometers over GPS systems?
The main benefit of accelerometers is that they can be used indoors. GPS can only be used outdoors as the signals would not be strong enough to penetrate buildings. GPS signals would also be affected by mountains and buildings, affecting accuracy on certain occasions.
The other benefit is that accelerometers generally require less battery to power as compared to GPS systems, thus being more energy efficient.
5) How much do accelerometers cost?
The top of the range accelerometers may cost as much as $800/-. see http://www.polaraustralia.com.au/au-en/products/maximize_performance/running_multisport/RS800CX
6) Where are the popular locations on the body to place accelerometers?
The location of the accelerometers is usually decided by the manufacturer. The most popular sites to place the device would include the foot(see http://www.polar.fi/en/products/accessories/S1_foot_pod), the wrist and the waist.