Distance Training

I think there’s something similar already?
http://en.wikibooks.org/wiki/The_Unicyclopedia

You could take one of the brakes off of an old bike. Or even just buy one brand new, V-Brakes aren’t expensive. You’ll need to rig up some kind of adaptor for the magura mounts, like this:

I’m pretty sure you can buy v-brake adaptors too.