My wife and I recently went to Death Valley National Park and while I was researching the area I discovered the Nation Park Service (NPS) mobile app. This is a really nice app that they keep up to date with the latest news and events in any of the National Parks in the U.S.
The best feature, in my opinion, is the offline mode and maps. For Death Valley in particular, there is no cell service so having the park map that shows your current location is invaluable.
There are a ton of other features like self guided tours and things to do that make this app great for any adventure you may make to a Nation Park.
See more details and download the app from their website: https://www.nps.gov