I recently came across this application called TSheets. It's a time tracking tool that is also integrated with Jott, which allows users to clock-in over the phone.

You can try a free 30-day trial of TSheets by going to the following page:
Employee Timesheets

You can access it on your iPhone or iPod Touch (over a WiFi connection for Touch users) at the following URL:
TSheets Mobile Time Tracking

I found this app through Tech Crunch article at:
TSheets Lets You Clock-in To Work From Your iPhone