Considering this forum is a website technical forum, a place for help with the iRV2 site, I won't attempt to answer the question about what Doran sells. However, I will post for iRV2 regarding the link on the home page.
That link connects to a screen on RVUpgrades
where the tire pressure monitor is offered for sale @$299, if you're interested in one please follow the link through and place your order.
I'll encourage you to start a new post in iRV2 General discussion regarding the Doran question, there may be members who don't view this area who know the answer.
If we can be of further assistance with a question about this site, don't hesitate to continue this thread.