API Access to Timesheets

It would be really helpful to have API access to time sheets, I'm trying to build an interface for my customers where they can see how much I've recorded in terms of time before I've billed them, give them the opportunity to "approve" a time sheet and then, ideally generate an invoice from the timesheet. I'm not asking ClearBooks to develop that functionality but instead to provide an API to time sheets so that I can write something on top of that to provide that capability.