I left the GPS in my car on the dashboard for a few days and it melted. It works fine...but it's all warped up. Don't leave it out in the sun...just a warning.

GREAT advice!
I live in Phoenix, so this is especially valuable as it gets HOT and SUNNY here. I'll try to get a thermometer inside my car to play with this a bit.

Tell me - what were the weather conditions and temperatures?

solution: solar-powered car cooler that clips over window.

No can do on this front. Solar coolers have the solar panel on the inside of the window and all my windows are tinted for UV blocking. It's kind of a requirement for living in Arizona. I've purchased one before and it didn't spin - even in direct sunlight.

I just saw one advertised with the panels on the outside. Of course, there's a theft risk...

When it gets to 118F on the OUTSIDE in the Phoenix summers, it's not all that much help. The better solution is to keep it out of direct sunlight and, preferably, get a full window screen to keep your whole dashboard out of direct sunlight.

It looks like 103F highs all weekend, so I'll see what kind of readings I can get with a thermometer.

Would the GPS work attached the underside of the dash, or inside the glove box or armrest? The Nokia GPS seemed to work when inside a house/apartment during the Thoughtfix unboxing, I wonder how sensitive it is inside a car but not directly visible to a window.

That all depends on how your car is built and what your normal GPS reception is like. I've accidentally left my receiver in my pocket and got signal. Today's receivers are meant to be quite sensitive, so you may luck out. I'll try even hiding the receiver under the passenger seat and seeing if I can get a signal.

If you could, I think that would be useful in order for prospective owners to get an idea of where it can be located and still work - obviously all cars will be different and it's unlikely to work if enclosed in a metal box (excluding the car itself!) but it would at least confirm the GPS doesn't have to be "out in the open" in order to work.

I assume leaving it under the seat or in an enclosed space would spare it from a total meltdown - as I live in the UK I'm somewhat unaccustomed to these high temperatures...

This looks handy. I just wish these devices would use Splashpower-type inductive recharging so that you can drop your keys on a plate in the hallway and the GPS recharges itself...