Why not just make your own sensors? An Arduino could easily use a low-rate serial connection with the calc's link port, and sensors with that can be quite complex and very low-cost, while still being quite small. (Imagine arduino mini, not arduino uno)
Well, I don't have the labstation cradle, so I would have to connect this to the RS232 port.
So I think I would need a C Lua addon (since ndless allow us to do this), but then it wouldn't work with the Vernier sensor...
I think it would be a lot of time spent for really few users.
If I have time and nothing more important to do, I might try this anyway.