@leader21 I think there are different integration options
- Integration with a Homematic LANGateway
- Integration with a Homematic USB Stick
- Integration with CUL with a homematic firmware. See also pimatic-coc for FS20
- roll your own
There may be limitations with some of the options listed above, e.g. most likely, encryption will not be supported by the firmware for CUL.
It may also be sensible to have look at imatic-max. Unfortunately, Max! and Homematic do not appear to be compatible, however, I suppose they have a lot in common.
EDIT: Using the FHEM firmware image, the CUL stick also supports Homematic a.k.a. BidCoS. So, pimatic-cos may be a good starting point. As the CUL-Stick is rather expensive you can also roll your own - see http://blog.gummibaer-tech.de/cul-stick-868433-im-selbstbau/