Time Tracking App with Alfred integration
I use Harvest to track time. It has a robust API. There is a command-line tool called hcl for interacting with Harvest time sheets.

I haven't bought the Alfred Powerpack myself, but I presume that since the Powerpack includes an interface to develop your own shell scripts to extend Alfred that it would be fairly straightforward to start/stop new tasks:

$ hcl start mytaskalias adding a new feature

$ hcl stop


You've inspired me to look into this for improving my workflow. I currently use the Harvest application which has a very handy menu bar control, but being able to start/stop a timer quickly from Alfred sounds like a nice option…