We use a Blue Ox Adventa tow bar and it has been a good product for us. The telescoping arms make hooking up your towed vehicle much easier.
As far as supplemental brakes, I'd suggest you read The Physics of Towed Vehicles
to help you make your own decision. Personally, I would never hit the road with a towed vehicle without supplemental brakes, but I guarantee you can find plenty of opposing opinions.
As far as the Brake Buddy, they are very popular brake systems because they are relatively easy to install. What I don't like about them is you have to drag the box out of wherever you store it and place it in your towed vehicle and connect the brake pedal and wires associated with the device every time you want to tow. While it's not a big deal, it seems less fun after doing it often and especially when it's raining and you have to hook up that stuff under the dash.
We use a Roadmaster Invisibrake
system on our '97 Wrangler. After a more complicated initial installation, it is always connected to the brakes, requires nothing inside the vehicle when hooking up, and only the normal tow bar, electrical, and safety chain attachments are required.
Another option that is less expensive and very effective from all reports is the ReadyBrake
. Personally, I don't like surge type braking, but it does the job when you need it.
Another company that makes systems that require no inside the vehicle hookups for towing after initial installation is M & G Engineering
and you may want to look at that system too.
As previously mentioned, the steering wheel lock if equiped must be disengaged, and you need to verify in your owners manual that your 2012 Liberty can be towed 4 down.
One last source you might find useful is the Towing Guide
. The vehicle information is only through 2011, but the information is valid otherwise.