The m-Unit is basically an electronic relay system that connects brakes, lights, starting (but not on our bikes), horn, indicators and other functions. It was principally designed for customs with dramatically simplified wiring possible. But when I bought it several years ago I did not realise this and proceeded to construct a standard-ish loom utilising original switch functions, so it became more complicated instead of simpler. The mkI as I found out was not waterproof so I bought a mkII version which is.
It's a clever piece of kit and allows such things as standard or soft glow indicators, indicators at varying levels of brightness as daylight running lights, flashing brake light or standard brake light, self-cancelling indicators (with various seconds until switch off), headlight permanently on but switched off until engine fires and so on. You have to go through a program step to dial it in to which functions you want. It can also be combined with their m-switch which is a multi function button running a single wire to the m-Unit. But that is for custom jobs, not for me.
All you need to know, and more:
http://motogadget.com/en/