Cell phone booster. It will not create a signal out of thin air, but in marginal signal areas it makes the phone usable. In good signal areas the booster with a MiFi card and Firestick allows us to stream movies.
Tire monitors. I like them. Pressure and temperature without having to stop the truck, and fish out my IR sensor gun and tire gauge.
Propane tank sensors. Handy when they work. Hard to keep them sending. They lose their syncing frequently and it is a PITA to get them working again. The tank levels are displayed on a base unit inside the rig or our phones.
Per DW's wishes I started carrying a PLB when out hiking, fishing, or mountain biking by myself. Also bear spray.
Some real handy phone apps out there now. The National Park Service app (free) shows information and maps for any National Park. Download and store on phone for non-cell coverage areas. The similar US Forest Service app for National Forests.
The free Avenza app has National Park maps from the Park brochure -- the same map they hand out at the entrance station or visitor center. Download it, and the phone GPS will track you along the Park roads. The NPS and FS OHV maps are free. They want money for most other maps. There are a lot of other mapping programs, but often want a subscription fee for what the FS and NPS apps do for free. I usually down the latest mapping app to check it out and end up deleting it because it offers the same functions (or fewer) as my existing apps.
Our local library is a member of a library net, and has tens of thousands of e-books available for download through the Libby app. We send them to our kindles via the cell booster and MiFi. Also audio books for the long driving days. Download to a phone and bluetooth the phone to the truck sound system. You can download from anywhere, accessing the library collections from anywhere in the country.
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So many campsites, so little time...
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