Create Invoices from Timesheets

I'd love the ability to creating invoices from timesheets. I typically have multiple tasks for a client project, and each month I send an invoice that has a line item for each timesheet entry, so they can see the day / task / hours.

I usually work at an set hourly rate, but sometimes a task has a set amount that's being charged. I’d love to be able to just select the timesheets and send them to an invoice.