An app like this would be super useful for planning longer ultramarathons on trails where the terrain is always variable.
I did a similar plan many times where I try to come up with a target time for each aid station on the race course and then during the race see how I perform against that - whether I am ahead or behind the plan.
The main problem is that as long as segments are based on distances, they aren’t going to be accurate and often deviate towards the end of the race. Perhaps for officially measured road races distances are accurate, but for trail races they are usually not. Towards the end of a race, distance that you have on your watch can easy be up to 5% off from the official distance, depending how accurately the official race distance was measured. Often, tace officials just use distance from CalTopo or other online mapping tool, and that is often way too short.
It would be super nice if segments were defined by waypoints on the navigation route and if Suunto supported an extension of navigation route that allows including timestamps. That would allow building on the estimated pacing plan right into the navigation route. Garmin does actually have that and the Pace Pro feature utilizes that, and some 3rd part tools like Ultrapacer can generate a plan that can be loaded on a Garmin watch.
I think a feature like this should be built-in, or at least have some built-in support - like an ability to load a timed GPX (GPX with relative timestamps) and tell you how much you are ahead of behind when following the route. Then more advanced apps could be built on top of that.
