Most Companies implement a time recording system of what their employees do while working, so that they can budget and plan properly how long it takes to implement systems or do a piece of work. While these are proven methods to getting accurate information in your company, I would like to suggest a another alternative. What would be the effect if key people on a rotation basis had to keep a blog (diary). Private or public I think it would produce some interesting results.
In the first instance it would allow other people to understand the person.
In the second it would allow one to understand the job.
Of course for financial planning there are some limitations but so long as not everybody is doing it at once it should be fine.