I've gone the external battery route. Does the job, but I would someday like to go with self-generated power. One thing is that if you're using a device for navigation, the battery can run down much faster. Being able to keep it charged while using it would be great. The other issue is that finding a place to plug in is just one more hassle you may not want to deal with at the end of the day. I've had good luck, but then I've also had to do things like leave my battery plugged in at the restroom or stashed behind a washing machine overnight. And if there's any thought of stealth camping (heaven forbid), an outlet is going to be hard to come by. The device the OP mentioned only has a few reviews, but they are positive. A way to protect your devices is to use an intermediate battery with the charger. Let the charger charge the battery, and let the battery charge your phone. That should smooth everything out. That's what I've wanted to do: charge a battery while I'm riding and use the battery to recharge my devices while I slept.