Check out RVIBrake II.
It was developed by the inventor of Brake Buddy, I believe. We have one and it is MUCH smaller than any of the other "brake system in a box" systems out there.
Hooks up in less than a minute, communicates to a wireless module in the coach so that you know when it applies the brakes and how much brake pressure is being used.
I can't recommend the toad tire pressure monitoring option offered by RVIBrake II. Mine has never worked, even after the company replaced the first set at no charge. It would be a great option, if it DID work.