Timers should correspond to Invoices
Currently you can track time but there's really no point to the timer feature if you can't connect that information to an invoice.
Harvest.com does a fantastic job of this, and it has a very simple UI which reminds me a lot of freedcamps.
It works as described with Invoices+. Invoices application is discontinued by us.
Angel Grablev commented
You can use our Invoices+ application from our Marketplace which does allow you to integrate time tasks with Invoices.