Thanks guys for your quick replies.
My concern is more when traveling or in the RV park. Our Yorkie used to be the best alarm as she was a yapper when she heard anything, but she is 16 now & doesn't bark at anything as she can't hear so well :) We have young daughters and have an alarm at home that gives us comfort when sleeping or away. We make lots of day trips, leaving the RV with our valuables inside at times.
I've researched Tattletale Alarm, and it looks good but costs $20 a mo. for text & email notification.
I'll look again at Simplisafe & check out Fortress - great suggestions.