I am looking at lp gas water heaters for my new house. I went to one store and they were out and said any new ones they get will contain a new safety device and cost $80 more. He didn't say what the safety device was.

Anybody know what this device is and should I get a newer safer one or the old stand by?

Yep your right! The new ones basically have a new safety sensor. The sensor shuts down the gas valve in the event of combustibles or fumes from them come too close to the water heater. You should be OK with a model without the new safety feature, but you better hurry, because all manufacturer's are mandated to install it.