2D:4D digit ratios are used for several health and business related applications. Currently, digit ratios are measured manually. This study proposes an automatic digit ratio measurement approach that can be used in the context of smart city healthcare and business applications. Smart city healthcare needs to be founded on the principles of self-service and independence. The proposed approach assumes that an image of the hands of a user is acquired using some imaging device. First, the hands are separated from the background. Next, the hand outline is traced. The hand outlines are used to identify points of interest that are used to measure the finger lengths and digit ratios. Experimental results are promising, but further research is needed before the approach can be deployed in real-world settings.