I want to detect if a seat is occupied by a person. This is [the answer][1] that I found on Stackoverflow. 

However, how accurate is the output of 4 suggested sensors? Will the computing of all these 4 sensor values into one boolean recognize a case when, for instance, a box of 40kg is placed on a seat and some person is just slightly "shaking" that seat with a hand? In those cases Arduino should recognize that a seat is not occupied by a person. Will it work with only 4 sensors or is there any better and more accurate solution (maybe some existing library)? I guess that CapSense-Library is not applicable in my case.

  [1]: http://arduino.stackexchange.com/questions/1288/detect-and-stream-if-a-chair-is-occupied/1308#1308