Working on some project related with video scrambling, I came across on this device: Gretacoder 101/102.
In two words, it provides two-dimensional scrambling: time and frequency domain and able to connect to telephone / radio link.
I thought it would be nice to have something like this, but with VoIP support and the ability to operate with SIP phones...
And as soon as I had some free time, I decided to start making prototype.

The first version have already done and supports:
  - based on emPBX and provides all of its basic functionality
  - key exchanging over DTMF
  - broken screambler ;)

More details will be available when time appears...