Yes! In particular, Harvest for Mac: http://www.getharvest.com/mac.

Killer features: - Start/stop timing in one-click or keyboard shortcut - See exact time in menu bar: https://www.dropbox.com/s/d56zb9ryffik7ey/Screenshot%202014-... - Idle time detection - leave your computer with timer running. When you're back, Harvest asks "You've been gone 15 minutes, should that time be counted?"

Still hoping for: - better offline support (can't stop timer w/o internet access, which means a bit of mental work when working offline on the Caltrain).