This is a classic. Making a check in front of your chin means "Great" or "All Good". As in, 'Hey, how are you?' and this gesture is demonstrated as a response.
And even though it is a very traditional gesture as well (some consider it to be old-fashioned), it might be my least favorite. If you ever see me make this gesture in your presence, I now (in documented writing) give you full-blown consent to smack my hand into my chin. Hard.