As we now have the source code for the Smart Chef Demo as well as a step-by-step GPIO tutorial, it should be possible to add new sensors onto the S3A7. There's also a walkthrough for the SK-S7G2 to connect it with the AMS Sensor.
Although I haven't gone through the GPIO tutorial myself, I asked an electrical engineer that is hacking on the board if he thought it would be easy to add another sensor onto the board.
This is what he had to say.
My understanding from talking with one of the engineers at Medium One was that it should be relatively straight forward to switch sensors, especially if the new sensor device uses one of the protocols already integrated into the SmartChef demo ( i.e. I2C). If your PH sensor is I2C, I think all the hooks are already present to handle data transfer and communications with the sensor. At minimum, you would need to dig into the code to adjust the I2C address that's being called. It may also be required to make a change in how the returned data is interpreted ( i.e. what is the format of the returned data ). After that, I think you might be able to post process that returned data using Medium One's Python scripts to display the result in the desired way (i.e. set a PH alarm etc).
I know that's not a very technical response but I honestly haven't had a chance to really dig in yet. If you or someone else in the community gets it working before I can dig into it, I'd definitely be interested in the specifics. I would still like to do something with a LIDAR sensor I have that uses and I2C interface and was counting on a "simple" integration.
If someone makes progress with this, please post your experience.