I show and compete with my dogs, and basically got my MH to use as a large dog transportation device (with amenities!). I often have to dry camp at events in hot weather with no shade, and had obvious concerns about leaving my dogs unattended in these conditions (genset running air conditioning). I recently purchased the AnimAlarm (see link below) and it works like a charm. It's basically a temperature sensor with a SIM card, so sends you a text message when the temperature parameters exceed the limits that you have set. I'm much more comfortable leaving my dogs unattended with this device. Many of the older units were radios, so had serious distance limitations. The AnimAlarm just needs a good enough cell signal to send a text message (which is a pretty low bar).
I'm a veterinarian and used to take care of my local state police dogs, and saw a trooper accidently cook his dog left in the cruiser with the engine and AC running. The AC failed, the car was still running (and looked fine from the outside) but the AC was blasting hot air. A very sad situation ... all the cops have temperature sensors in their cruisers now. The AnimAlarm is the first dependable, cost-effective temperature monitoring system that I've seen.
Cost was $170 (shipping included), then you have to get an AT&T or TMobile SIM card. I have a GoPhone pay-as-you-go plan that was $25 for 3 months of unlimited texts. It will text any phone that's paired with the device (I use Verizon for my personal phone).
http://crittercozy.com/Household-Safety/animalarm-temperature-sensor.shtml
