Google has a way to send specific instructions to email addresses of your choosing if you don't log in for a set amount of time. Otherwise I'd recommend instructions in a will as suggested already.

As for other people taking your calls at work...that's a weird setup you guys have there...

*edit*

I should also note that I can't think of a scenario where you couldn't just have a PIN code and share it with the people who might need to get into the phone...