I was a little confused at first about there being only one wire attached. But upon further thought, and reviewing all the pics on the website given, I realized that they are designed to be wired in series. The axel, or at least one wheel, of each unit picks up one rail, and by mounting them in opposite orientation and connecting the wires of each together, the motors are then in series with each other. Clever, but doesn't lend itself well to DCC.
I like the idea and can see many applications for such a unit, but probably still in the future for most applications. It's designed for single cars (street cars, RDCs, etc.) and would likely not have enough power to pull much, even if you put four of them in a single diesel unit. But in time I think these types of units will break that power barrier, and then the increase of available space inside a diesel shell will present fantastic new opportunities.
Interesting that they say it's 1/80th scale. In that scale, a 10.5mm wheel scales to 33". But, in 1/87th scale 10.5mm scales to 36", a really great choice for those of us who run EMD E-units.