travel with dog in trailer?

We tried this for the first time over Memorial Day Weekend. We did not have room in the truck for our 70lb Golden Retriever along with our children. So we strapped down a crate where she is used to being in and checked on her frequently-almost every hour and she did wonderfully. The trailer stayed cool (We ran the A/C before leaving. Even when we travel in our family vehicle she is placed in a crate for travel. It can be quite distracting to have large dog roaming the vehicle-not to mention that if we were to have to suddenly stop she could go flying through the vehicle.

I like the idea of a monitoring system-it would put my mind at ease and also running a 12V fan.