1. A method of transforming optical signals into indicators indicative of a respiration rate, the method comprising: receiving optical signals from an optical sensor; transforming the optical signals to a series of signal data points; filtering the signal data points to remove data points caused from noise and artifacts; checking signal quality of the filtered signal data points by comparing the filtered signal data points against a predetermined signal quality criteria, if the signal quality does not meet the predetermined signal quality criteria, repeating the steps above, if the signal quality meets the predetermined signal quality criteria, proceeding with the steps below; detecting a series of peaks or valleys for the filtered signal data points; determining the time difference between individual peaks or valleys of the series of peaks or valleys to produce a series of time difference values; detecting peaks or valleys for the series of time difference values; determining widths between the peaks or valleys of the series of time difference values; estimating a respiration rate from the widths between the peaks or valleys of the series of time difference values; converting the estimation of a respiration rate to a indicator indicative of a respiration rate, and storing the estimation of respiration rate in a memory of a device.