Break away brakes as mentioned earlier, have a 12V battery, that when a switch is triggered (Via a cable connected to the towing vehicle) it locks the trailer brakes on as hard as it can.
I have only EVER seen them as an electric setup, I do not believe that there is an electro-hydraulic version.
If you upgrade the brake system to break aways, you still need to have the axles, rims and tyres rated to the higher limit.
This is done by checking manufacturer specs on the tyres and rims, and than the axles are weight loaded depending on their size.
You then also need to do upgrades to things like chain linkages etc.
Electric brakes, while more expensive, are leaps and bounds ahead of the normal cruddy mechanical brake system.