The COROS Performance Optimisation Device (POD) is a useful technical addition, designed to gauge and improve running form by collecting a number of metrics not measured by most sports watches.
A ratio of speed to power-to-weight measures how much energy is involved in forward propulsion; an increase in speed but a drop in power, shows an improvement in running efficiency. The POD records this metric, which can be used to work on developing a low power, optimal technique.
The POD can take away some of the guess work in judging effort by calculating running power. Taking into account your weight, speed and several other inputs will calculate your Running Power laterally, vertically and most importantly horizontally (forward propulsion). Running Power along with other key metrics like HR is a great tool to measure effort, as it will take more power to run uphill as it does to run the same pace on flat terrain.
The POD introduces new metrics like Stride Height, Ground Contact Time and Left/Right Balance to detect running form. This allows runners to work on their ground contact time and work towards a more optimal cadence for their body dimensions and weight. The left/right balance metric might be used to judge injury on one side or compensatory running form.
The POD can be paired with the COROS app on a phone and used without a watch to collect data which can be browsed later and also integrated with tools such as Strava. Note that using the POD with a phone will significantly increase the phone battery consumption.