[tehwebguy]

From the FAQ:

Q. Can I lock my Coin?

A. Currently you cannot lock your Coin, but you don’t have to. Coin will automatically deactivate if it loses contact with your phone for a period of time that you configure in the Coin mobile app.

Bummer! Seems like there should be a way to use your phone to lock it down. Either way this is cool as hell.

[timharding]

You could turn off bluetooth, that would lock Coin, after a period.