Ah, I see what you mean. I looked through that project and back at the S4 USB API document and it looks like they just never pull speed or distance from the memory. It looks like those fields can be accessed with the IR command (their this.readMemoryAddress function). Although, it looks like others don’t necessarily trust the distance, but it could be worked around with the calculation they mention.
I tried to find out what Bluetooth sensor specifications Suunto watches support but couldn’t really tell. I’m also not that familiar with how Bluetooth sensors usually work, so maybe it all comes down to what the existing software supports. I also don’t know anything about rowing tech, so maybe this is already solved.
If I had the equipment lying around the house I’d definitely hack up those pieces missing from the project. I think it could be done in not too much time and it’d be a fun project. Unfortunately, my wife will definitely put the foot down to another watch or rowing machine entering this house.