USB car chargers are common, but less so are ones that keep charging your gear when the car is off, or that can double as an external battery pack. The Nomad RoadTrip is both: It will charge your phone while you drive, but it will also keep your phone juiced with its built in 3000mAh battery.
The Roadtrip will set you back $90. The concept is pretty simple, but I was sceptical until I tried it out. I mean, if you're charging your phone in the car, you probably don't need that charger to also have a battery, right? Well, that's true -- but if you have a car that won't charge if the keys are out of the ignition or the engine isn't on, a near-dead phone, and you need to run into the store for something, the RoadTrip will keep charging while you're gone, and then pick up from the engine when you get back to the car (and recharge itself in the process). That might be a niche case, but I can just as easily see myself charging while I drive somewhere, not getting a full charge, and then taking the RoadTrip and sliding it into my pocket to continue charging while I'm out and about. Either way, your phone gets charged.
The RoadTrip isn't perfect though. It has two charging ports (a slow 1.5A each.) One is standard USB and the other is USB-C, which means you have to have a specific combination of devices (or cables) to charge two things at once. It also only recharges from your car, so you can't use it and plug it into a wall to charge the internal battery. If you usually drive from one place with an outlet to another place with an outlet, or never leave your phone (or other device) in the car for anything, much less to charge, it's probably not for you. Still, for those folks who can see the utility in a car charger and a battery in one device, or want one less thing to carry around, it's worth a look.
Roadtrip for iPhone and Android ($90) [Nomad]