I've seen this app around here a couple of times, I think, but my extensive searching has come to naught.
I think it has a GUI in the form of a table, with rows being time and columns being projects (or the other way round). There are buttons which represent small chunks of time (10 mins) and you click on them under the project column to show what you are doing during that time-chunk.
Off to search LifeHacker now, in case that was where I saw it...