I use a 20 line Python script to convert Outlook .ics calendars into billable hour count. It looks for a company name (the client) and calculates start and end time. All it needs now is to fill a .pdf invoice template and I can get rid of HR :D
Shameless plug: I’m working on FormAPI [1], which can help you set up the PDF invoice template. We provide a Python client library, so you can add that to your script with a few lines of code.