I also have two and thought about it as well. Should be trivial to add.
With my Mixergy, we don’t have a temperature probe, we just show % SOC of the cylinder, 75%.
I’d be very cheeky to ask for a ‘Mixergy alternative’. 
For display only that’s easy, the standby losses are a different story, for those I need a temperature to subtract the ambient room temperature from. But maybe display would be enough for now?
