1. A computer-implemented method for estimating frailty, the method comprising: receiving a first reference frailty index value associated with a first individual, a second reference frailty index value associated with a second individual; receiving a first set of inertial sensor data associated with the first individual and a second set of inertial sensor data associated with the second individual, wherein the first set of inertial sensor data and second set of inertial sensor data comprise angular velocity data and acceleration data; generating a linear regression model that outputs a first frailty value estimate based on the first set of inertial sensor data and that outputs a second frailty value estimate based on the second set of inertial sensor data; and storing the linear regression model in a non-transitory computer-readable medium, wherein the linear regression model is based on the difference between the first frailty value estimate and the first reference index value and based on the difference between the second frailty value estimate and the second reference index value.