Nexave Deluxe Roller Brake
I'm running the Shimano Nexave deluxe roller brake for the Nexus hub. This brake can be added to any Nexus hub.
Rear brake lever
I have three brake levers on my trike so that I can work each brake individually.
The Nexave Deluxe Roller Brake connects to the frame by means of a bolted strap. This counteracts the braking torque. I have the brake set up to engage and lock up pretty quick, since my main use of the rear brake is sliding/skidding around corners. The Nexave brake does have very subtle control and can also be used to stabilize the trike at high speeds.
On the left handlebar I have the brake levers for the front left brake and the rear brake. I have the rear brake angled in slightly so that I don't use it except deliberately. The spacing between the two levers is such that I can use either brake individually, or grab them both at the same time.