For quick communications we have iMessage and a host of other messaging apps, each with varying degrees of security. Apple has claimed iMessage is extremely secure, but that claim has been questioned. Wickr says it can top them all with a free iOS app containing military grade encryption (AES256, ECDH521, RSA4096 TLS). Even better, the Wickr servers do not have the keys to decrypt your messages.
You can also set expirations on messages so they'll disappear after a pre-determined amount of time. Just like iMessage and most other messaging apps, there is no charge for the Wickr service, the app is free,
