derH2o,
I have been the Product Development Manager for Roadmaster since 1978, and was the sole developer for each of our braking systems. We research all new vehicles extensively and have no reason to believe there are any issues with any of our systems working on a 2012 Ford Focus with a manual transmission. However, the automatic transmission requires the battery to be disconnected, per Ford's engineers. So if you have an automatic transmission, you will need to disconnect the battery, which kills the power and the power source for the braking system will have to come from a 12-volt outlet kit and a stoplight switch kit in order to use one of our braking systems.
Please note that Ford's engineers have asked us NOT to recommend our automatic battery disconnect on this vehicle due to the steps that the vehicle goes through in preparation for towing.
If you have any specific concerns about this, please feel free to PM me or call our tech support at 800-669-9690.
Mike Cannon
Product Development Manager
Roadmaster, Inc.