I've found the necessary tire pressure gauge and air chuck to check and fill the tires on My Seneca. It's also on a Freightliner chassis. They both need to be straight and not offset. I got them at the local O'Reilly's.
I'm not a fan of the extensions. Seen them leak and cause problems.
The tire pressure monitors seem to have issues based on the research I've done. They need to be installed with sealant tape on the treads and may cause the metal valve on the wheel to crack and break due to the rotational force when the coach is driven. Kind of a personal issue but there's what my opinion is for what it's worth.
Good luck. Happy Motoring!