Pretty cool and it will cost us "Nothing"

How about two trains that take turns stopping at the same station.  They travel in opposite  directions and they always keep to the right as they enter the station stop.   After they have taken the correct track they automatically start up the other train waiting at the station and then they come to a stop themselves.  No magnets, sensors, diodes or expensive electronics needed.  There is always continuous action plus one train gets to rest while the other is moving.   This will also work well on an Interactive button as it can start up and shut down at any point in the cycle without causing a problem!

All you need to do this is 4 plastic track insulators and 2 simple O gauge TAD's or track activation devices that are used to change a signal from red to green.   The switches could be electrically controlled with two more TAD's or use the simple manual spring return as we did with the Sawmill.  That also worked very well.

The trick is you need one special engine that has a "polarity switch" on it.  Bachmann provides these on the Thomas and Friends engines we already have, plus it is also on the yellow Bachmann switcher engine (45 ton diesel)  we ran at the Mall which now belongs to the Club.

                                                              Click to enlarge image

Lots of action, easy to wire, and simple principles like the weight of one train completes a contact that starts up the other.  I love simple stuff that works!