An excellent idea for people who ride with their *pets, especially on hills.
An upgrade to this might be to make a flexible quick connection to the rear brake cable so it would just operate using the normal rear brake lever, although using your ass to stop is hilarious and fun.

I must admit, from the title, I expected something more like the flexigrip controls on Mr/s Garrison's 'IT'.

Adding video to channels (Pets) - requested by newtboy.

Yep, either a separate brake lever you can clip on and off or some way of hooking it into the existing brake system would be far better. Butts just don't have the response time, to say nothing of the ungainly pose needed.

I'd just set up an inertial surge brake.

http://bicycles.stackexchange.com/questions/25756/how-to-build-surge-brakes-on-bike-trailer

That way, you can concentrate on emergency stopping rather than spanking yourself...

I haven't tried it, but the butt brake lever seems to me to fit the application pretty well. Cyclists needing quick braking develop the habit of shift backwards on the saddle, or over the back of the saddle anyway. This helps to counteract the unweighting of the rear wheel that occurs with heavy brake application.

With the butt brake, an existing reflex is repurposed -- clever.

Others have certainly done that, so it can be made to work.

I don't think emergency stopping is the only application, though; it looks like the inventor uses her brake routinely.

Butt brake, USED.

Love it. This is a great idea for anybody with a trailer whether dog or baby.

BRAKE. Sorry, that's one spell checkism that sends me nuts.