TXTcrypt is a general purpose text encryption application for sms/email/notes etc. focused on ease of use and interoperability between mobile and desktop versions.
You can use it for text in any application , including text from the TXTcrypt desktop application.
Say you want to send a sms that only someone knowing a password for it can understand , or just need to encrypt a conversation to hide it for prying eyes , now there is a easy way for that on a iphone.
With TXTcrypt just enter your message and a password for it , now the encrypted message can only be decoded with that password , just tell it to someone , and send them message encrypted with it , they can use TXTcrypt to decode it.
TXTcrypt works with any character set being unicode compliant , the encryption used is as strong as encryption export regulations allow , not military grade but namely RC4 with keys as big as 64bit depending on the length of your password as such providing a decent amount of security.