Don't know if anyone has seen these or commented on them on the forum...
These appeared in Voie Libre this edition, and I thought they may be of interest -
There is a range of different attachments available. They are not automatic de-coupling (hand-of-god required) but couple auto.
Seems a good idea, I remember a toy train that used a similar magnetic system.
What do you think
Also whilst browsing their web-site saw these -
These appear pretty good, but probably only plastic gears. But if you want a really small drive unit these could be useful
Hope this is useful, David