Monitors are Pendulum-Servo vanes. That's the proper name for the type and there are a whole bunch of manufacturers of that type of vane including the Aries
which the Monitor was copied from. I had a monitor on my boat but it didn't interface with the wheel well. It just wouldn't steer the boat below four knots boat speed. I've done an informal survey
with a number of boats with PS systems and wheels and the results have been mixed. Some say theirs work just great others have light air/low boat speed issues. Looks like you pays your money
and takes your chances. From personal experience, a pendulum-servo system will steer a tiller steered boat even if the helm
is heavy, has a bad weather helm
, etc. A PS system would be my number one choice if I had a tiller. Wheels are yuppie affected abominations, anyway.
An auxillary rudder vane requires a really strong mount because they actually steer the boat just like the boats rudder. Something that would be a real challenge to build on a boat with a boomkin, outboard
rudder or other impediment on the stern. Most of them are made to bolt onto a flat transom and are easy to mount there. Your choice whether you want or need to reinforce the transom to take the load. WindPilot Pacific Plus and Hydrovane
are two manufacturers of auxillary rudder vanes. I've got the WP Pacific Plus on my boat and just did a TransPac with it. Worked great running wing and wing at near hull speed
for 12 days. The WPPP uses a Servo-Pendulum vane to supply the muscle to turn the vane's steering
rudder. Gives plenty of oomph to steer the boat especially in light air or running when the relative wind flowing across the wind vane is low.
Look for a used vane. They show up regularly in any major boating
area. Sold my Monitor for $1700 with wheel adapter. Bought the WPPP for $1800 in San Francisco
. Monitors come up all the time. Lesser known or less popular vanes are hit and miss. Scanmar will sell you the mounts and tubing to adapt the Monitor to almost any boat. Since they are so popular, they have data on mounting their vanes on a ton of different boats. The thin wall stainless tubing and most accessories, like the wheel adapter are quite pricey, though.