Innuendo

You know how to give and understand secret messages while appearing to be speaking about other things. Two rogues, for example, might seem to be talking about baked goods when they're really planning how to break into the evil wizard's laboratory.

You can get a message across to another character with the Innuendo skill. The DC for a basic message is 10. The DC rises for complex or new information. The person attempting to receive your message must also make a check to interpret your message. Third parties overhearing your message may attempt to intercept its meaning by making an opposed roll and beating your check to send the message.
If the check fails by 5 or more, some incorrect conclusion about the message has been inferred or implied.
The DM rolls your check, so you don't know whether you succeeded or missed by 5 or more.

Generally, retries are allowed when trying to send a message, but not when receiving or intercepting one. Each retry carries the risk of miscommunication.

If you have 5 or more ranks in Bluff, you get a +2 bonus on your check to transmit (but not receive) a message. If you have 5 or more ranks in Sense Motive, you get a +2 bonus on your check to receive or intercept (but not transmit) a message.