I keep a small $99 14 MP point and shoot in my car (actually RC go bag) to document traffic accidents, fire scenes / damage etc. Its a LiIon battery because the latest P&S seem too slim for AA batts - and that's fine, because the P&S has only been charged once in 2 years of ownership. Get a larger microSD or SD card than you'll ever need, and you're not exceeding some limit on documentation. I also travel with the same camera, and having a USB output cable or wireless out means you can download and send off pix as soon as you take them, even porting them over to your phone for fast emailing. I don't cart the lion charger around but I could easily, and charge from the car. Picture quality and detail are also better than my smartphone camera - important if you're documenting loss after a disaster or trying to communicate to someone else your damage assessment (combining word art + camera photos). And the video options are important too - you can take pictures, but equally important may be taking a video of the other driver, with their slurred speech, angry or aggressive attitudes etc. Always good for a laugh when appearing on Judge Judy!

Smartphone camera is pretty good but smartphone power is less than 10 hours. Like I said my dedicated P&S hasn't run out of power on me yet.

Use it a lot actually. Nice to have but not an essential.