Try the auto-delete feature on BBM

The recipient has a 5s or 10s or a time to read the message then the message content will no longer be viewable.

This feature is similar to that of Snapchat and is equipped with BlackBerry for BBM in recent updates. If you feel the need for confidential content, this is a good way. BBM is now available both on Android and iOS, so we can use this service right away. Windows Phone has BBM but does not support this feature, ie you send to BBM on WP is not hidden and vice versa.