Was asked about this today offline and thought I would post here...
One of the devices I brought into use on my track powered layout was one of these:
http://www.rayman4449.com/Power_remote-cutoff.htm - GE Smart Remote plus outdoor outlet receiver
A remote control that serves as an emergency cut-off to the entire layout in the event of an accident. I have found through time this is one of the best aspects to running track power is that in the event of a derailment I can instantly stop all trains at the same time as every second counts to limit/prevent damage.
Another version that I have found that seems to work good too is the Clarion Outdoor outlet control (model: HW2190L)
Raymond