Hello @John-Brindle,
You should be able to find detailed information about UniPi 1.1 on our website. Based on your questions you may get more mileage out of our Neuron models, as the UniPi 1.1 only has a limited number of inputs and outputs. It also lacks the capability to measure current.
We supply a standard-compliant 1Wire master with an OWFS interface, which means that if you are willing to write your own software support for your 1Wire-compliant device it will work. The MAX31850K-1 however appears to use a 1Wire-like protocol instead of true 1Wire; based on information I can find it ought to be compatible, as we simply provide a fully standard-compliant 1Wire master, but I cannot guarantee it.
In terms of third-party devices the question is in practice about the communication interface they use, rather than their nature. As such while UniPi devices will work with e.g. many flow meters, they will certainly not function with all devices of that class on the market.
I'd encourage you to peruse our documentation further and see if the unit fits your specific use, particularly with the number of I/Os, and to perhaps look at our other offerings as well to see whether they would not be a better fit.
I hope this helps