OmniFocus to OmniOutliner Time Tracker script
 

Here is a solution for time tracking integrated with OmniFocus. It takes the currently selected task or project, and logs start and stop times in OmniFocus. I have it setup as a button in the toolbar in OmniFocus which works well.

Known limitations:
[LIST][*]The front-most OmniOutliner document is used. The script probably needs to save a preference pointing to the document to use.[*]A modal dialog is displayed in OmniFocus to stop the timer. This means that you can't interact with OmniFocus in any way until you stop the timer. I have a few ideas for addressing this, but suggestions are welcome[*]It needs a nice icon (I personally am using the Clock icon that ships with Ubuntu's Gnome)[/LIST]

Thanks for this! I tried this out today instead of using the software Project Calculator. I actually don't mind it locking OF - if you are working on the task you are not working on OF (unless that is the task....). The only thing that I missed compared to PC is the time worked on that task. I added a column and worked it out with a calculator! :)

Glad to hear it's working for someone else. For calculations, I generally export my OminOutliner document to CSV, and use a spreadsheet to do them. But, it should be pretty simple to add such a function to the AppleScript itself, so perhaps I'll do that.