One thing that I think any traveler really needs is a powerbank!
I bought a 35€ powerbank before going on my vacations, and without it I'm not sure how I would have made it...
I had to always have location and google Maps on while moving around, plus the videos I took and going through the web made my phone's battery just quickly drain!
And since I only spent a few hours per day in our airbnb, it almost didn't have time to charge the phone and powerbank fully.