The last 8 years I am working on contracts on remote and for the clients that are charging by hours, it would require to send invoices hourly every 2 weeks. I was trying to use the different applications for invoicing but then moved away and used google docs to build it.
Then I found Wunderlist, nice todo list application. I created Shopping and TODO lists and started to use daily. as result it became like a habit for me to write there. I decided that it would be awesome to track my hours there as well.
Example format for task hours:
After month I decided to download this list and calculate hours that spent for the month. As result I did the script for downloading the hours report into csv file