I don't have the name with me on the road, but you can get a valve stem for the outside dual so that it faces out instead of in. Very easy to use the tire monitors.
I have the TST system as well. I recently upgraded to the 507 unit with the replacable batteries, but I stuck with the cap type monitor instead of the flow through style, I rarely need to add air. I use the extender, but it is not always necessary. With the extender I was able to read the toad pressures when it was being driven a ways behind the coach! I just wired it to simply plug into the cigarette lighter on the Honda. No permanent mounting.
The system is not cheap, but well worth it for the convenience and peace of mind. Very accurate. The unit reads the pressure to the pound as my digital tire pressure guage.
'04 Alpine Coach 36' MDDS