Hi, You might also like to checkout http://yanomo.com. It can import your Google Calendars so you can log time to your appointments. Like you say "...they are not necessarily good timekeepers". Having your planned day as a guideline to log your hours makes is a lot easier, quicker and more accurate.
It is also available as a Google Marketplace app: http://www.google.com/enterprise/marketplace/viewListing?productListingId=8955+4306296467348698182.
Joost - CTO Yanomo.com
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