Anyone know of a timecard app that uses GPS? I'd like to log the hours I'm at work using the GPS on my iPhone. (It'd start logging when I get to work, then stop when I leave for lunch, etc)

If possible, I'd like to be able to log the time at multiple locations, so I could see for each day time at home ~12h, work ~9h, commuting ~3h
Another app that does this in a more generic, passive, long-term fashion is Placeme.