I ended up using my RPI 3 to run homebridge and used the script plugin to contact my omega2+.

The on script: ssh root@omega-ABCD.local "relay-exp 0 1"
The off script: ssh root@omega-ABCD.local "relay-exp 0 0"

Initially the delay was noticeable due to the new ssh connection every time but then I used the ControlMaster feature of OpenSSH, which opens a unix domain socket for the first connection and reuses this connection in all subsequent calls.

The achieve this you should place this in your ~/.ssh/config of the RPI 3 that will contact the omega2+:

Host * ControlMaster auto ControlPath ~/.ssh/master-%r@%h:%p # I chose to persist it for 5 days ControlPersist 432000s

It is now very responsive and I don't wast a full RPI to this single button