I was originally considering openhab, but then I discovered Home-Assistant (https://home-assistant.io/) and I've been hooked since. It ticks off a bunch of check-boxes that made it a great home OSS solution:

Pro's

- No internet required, can run entirely on a Rasberry Pi

- Integrates with most everything thanks to the huge component library (https://home-assistant.io/components/)

- Easy to write your own Python component to integrate with new stuff

- Can use existing SmartThings/etc hubs or Z-wave usb stick to talk to most anything

- Fairly easy to write automations

- Well written Python 3 code-base that's fairly easy to read and see what's going on yourself

Con's

- Definitely more for the DIY tinkerer

- Need to write YAML for the automations, though a new GUI makes this easier for many cases

Setting up an SMS to me when a motion sensor tripped was pretty easy, my automation was:

    - alias: Alerting on bedroom motion
           initial_state: False
           trigger:
             platform: numeric_state
             entity_id: sensor.bedroom_burglar
             above: 0
           action:
             - service: notify.aws_sns
               data: 
                 message: "Bedroom alarm sensor has been tripped!"
                 target: HassAlert

I've had it running for over a year now, and it's been quite nice.