I would like to know how does apps like Torque calculate if my car (Hyundai i10 Era) is 'Not ready' yet? What are the factors (complete list) do one checks to decide? Is there any formula to calculate readiness (which I guess, there is none)
There are not calculations. The car has a list of PIDs that the tool checks.
The readiness monitors are a set of tests that the car runs including but not limited to EVAP, EGR, CATALIST, O2, FUEL, COMPREHENSIVE. When the codes in a car are cleared all the PID values for the monitors are cleared. As the car completes and passes the necessary tests it will set the PID values to pass.
The scan tool or App does nothing other than just reads the values.