I do not know whether I am reinventing the wheel, but I have never come across the following reporting method.
I imagine that if I was to choose a single metric to report to upper management about a project, it would be the risk of the project not delivering something of the intended value, on time. I imagine that this metric could be used on something like a project webpage.
In the beginning of a project, I would, as as project manager, set it to a conservative 50%. The goal of the group is to to reduce the risk of failure. I imagine that on such a project page, there would be a deeper description of why it is set to its current value. This could be: Risk of misunderstanding between senior management and project manager, risk that a larger project in a different part of the organization will make this project obsolete, risk of not having the needed critical resources available throughout the project.
The reason why I believe that this is the single most important metric, is because it will quickly give senior management the one metric, which is important when deciding whether to use their capacities on the project, either by stopping it, redefining it, adding resources or something else.
Is this just old theory, or is it new?