I second the recommendation for an EMS-HW30C. This way, there is no portable device to lose or get stolen, and low voltage can destroy A/C compressors just as badly as overvoltage (the EMS will shut power off if voltage goes too low for a period of time.) If a hard-wired EMS is a no go, go for the EMS-PT30C and a long steel cable + padlock. If one does have an EMS, it can't hurt to have an external surge protector anyway (SSP-30), just so it takes the lightning strike and not the more expensive stuff.
The only real reason I've not gone with an EMS myself is because I plan to sell/trade my current rig in later this year.
The EMS will more than pay for itself the first time you plug into a 240 volt miswired outlet and see an "E-3" code on the display, as opposed to having electrical components fry, or even worse, the RV barbecue itself.