My favorite GPS app for mobile is Gaia GPS: https://play.google.com/store/apps/details?id=com.trailbehind.android.gaiagps.pro&hl=en. It's $20, so not cheap (at least compared to apps, still much cheaper than a dedicated GPS device), but it allows you to load in GPX files and also download base maps from a wide array of sources (topos, aerials, etc) for offline use.

You can also load GPX files through the web interface and it syncs with the app. You can save waypoints, routes, tracks, photos, etc. that sync with the site.

I am not involved in SAR, but backpack and hike a lot. I really like Gaia GPS app. It was a one time $10 fee (never mind looks like it's $20 now). Very highly reviewed - I've never had any reasons to complain about it!

You can download and pre cache full resolution USGS topo maps for any custom sized areas you want.

https://itunes.apple.com/us/app/gaia-gps-topo-maps-hiking/id329127297?mt=8

https://play.google.com/store/apps/details?id=com.trailbehind.android.gaiagps.pro&hl=en

Gaia GPS. You have to pay for it to get "premium overlays", but it's worth it, great app for navigating and tracking.

https://play.google.com/store/apps/details?id=com.trailbehind.android.gaiagps.pro&hl=en_US

Mtn Hub also is good, has a community of backcountry users, but it's better for getting conditions reports than for mapping a route

https://play.google.com/store/apps/details?id=com.avatech.mountainhub.prod

I think it's free to get slope angle, aspect, etc

I'm assuming you want this for driving so +1 for offline Google maps download. In case you want it for hiking I recommend Gaia GPS although it is $20

You can check here, also download the app Gaia GPS

Gaia GPS. You can track your routes, color code each one and put each track into different folders for organizing. I use it to plan drives, points of interest and to see where I've been

I use Gaia GPS with its free "Gaia Topo" map download. And a fat charger battery, just in case.

for iOS

for Android

Public tracks are now available in the app. Please upgrade to version 2021.2 in the App Store (iOS) or version 2021.1 in the Play Store (Android) and you will be able to turn on Public Tracks in your Map Overlays just like on the website. In iOS, tap Layers > Map Overlay > toggle on Public Tracks. In Android, tap Layers > scroll down > toggle on Public Tracks.

Public tracks are now available in the app. Please upgrade to version 2021.2 in the App Store (iOS) or version 2021.1 in the Play Store (Android) and you will be able to turn on Public Tracks in your Map Overlays just like on the website. In iOS, tap Layers > Map Overlay > toggle on Public Tracks. In Android, tap Layers > scroll down > toggle on Public Tracks.

This is a list of items to consider in a car kit. It is by no means complete, and is meant to be inexpensive and good rather than expensive and great. Substitute whatever you know to be better.

Preparation

• $0 - Research.
• $10-20 - Area map and quality compass.
• $20 - (Optional) Gaia GPS Pro with cached map of the area.

Communication

• $0 - Tell people your plan, include details.
• $1 - Pen & paper. Leave a note in your car.
• $5 - Bright color duct tape
• $9 - Bring your fully charged cell phone, and battery to charge it with
• $6 - (optional) Small mirror or signal mirror
• $8 - (optional) Signaling whistle

Safety

• $0 - Common sense. Be cautious and careful.
• $15 - Fixed blade knife
• $9 - Headlamp, and a spare set of batteries. Substitute your existing or favorite for this.
• $5 - Home made first aid kit. Take a quart sized zip-lock freezer bag and add whatever you have from home to include band-aids, moleskin, dressing, tape, butterfly closure, alcohol or antiseptic wipes, bite/burn/antiseptic creams, aspirin and an antihistamine. If you want to buy a kit off the shelf, customize it and be familiar with what it does and does not have in it. Adventure Medical Kits have a good lineup.

Warmth

• $0 - Wear appropriate clothing, including appropriate footwear. This is vitally important.
• $0 - $10 - Old hat, old socks, gloves in the car.
• $10 - A tarp
• $1 - A few trash bags to use as rain ponchos 1
• $8 - Sleeping bag, blanket or mylar blankets 1. This is assuming car shelter or built shelter.
• $4 - Two full sized Bic butane lighters. Full size Bic's because of the square/cube law (a lot more fuel) and they are much easier to light with cold hands.
• $7 - Good matches of any kind, though preferably storm matches.
• $1 - Petroleum impregnated cotton balls. Starting a fire with everything wet can be hard.

Hydration

• $0-$10 - Bottles of water in your car. Can be $0 if you fill any container yourself. You can also include sports drinks like Gatorade, Powerade, etc.
  
• $20 - Sawyer water filter. Better than the lifestraw.
• $11 - (optional) Metal bottle. Stainless steel, single walled, no insulation and no plastic when the lid is removed will allow you to boil water.

Self-rescue

• $19 - Backpack to carry your kit in.
• $20 - Basic car tools. A couple of hose clamps, multi-head screwdriver, two crescent wrenches. You should also have jumper cables and a quart of oil. Know what your particular car needs from its current issues or past issues.

Miscellaneous

• $7 - (optional) Food. Most any snack food or energy bars like Clif. This is solely for comfort and to prevent you from trying to gather or capture food which can increase risk and calorie expenditure with no guaranteed return. You should only be eating if you have abundant water, so things like Knorr dehydrated noodles are good. Almost anything dehydrated that you need to boil water to hydrate will do so with cold water, it just takes longer.

GaiaGPS