tire presure would be insane... my caddy has transmitters in the wheels that transmit there own unique identifier code along with a preasure reading whenever they spin & transmit all throughout the driving time & stay on for a while after you stop, you can see the actual preasure, that would be really cool,I would definatley want to do this in my montana if this is possible, I think all 4 transmitters cost me around $175 though wholesale, & I don't know what would be needed as a reciever or software wise, but this would be a hit for sure, considering the pro rv systems are over $300
servo's, although you did say that's later, would be awsome too.
as far as accessories, one that comes to mind is a current flow reading device, IE a shunt... you could use 25 amp & 50 amp modules, these could go in line with the desired device that you want to monitor
just a thought...
Different sets of HVAC controllers... for the 3 major types of HVACs I'm always reading about on here... fully electrical, pressurised/mechanical, and the ones in between.
That is if memory serves me correctly