The worst thing that could happen to you nowadays is that your smartphone runs out of charge. I faced a similar issue on a road trip where for the entire trip I had to keep my iPhone GPS on for Google Maps. Very soon my phone's battery got drained. And I have a habit of forgetting to take my iPhone cable. Thankfully the month before I had got a NOMAD charge key which saved the day.
NOMAD Charge Key for Lightning and Micro USB Smartphones
It is a very small and portable cable for your iPhone. It also has a micro-usb version which can charge and sync android and windows phones. These ChargeKeys are shaped like any house keys so you can carry them along with your other keys. This way you will always have a charging cable ready whenever needed.
Any USB power source will work, like laptops, car audio USB port, portable chargers etc. Regular charging cables gets tangled and very hard to carry by itself, unless you are have a bag, sometimes you might forget also. Nomad ChargeKey is much easier to carry and it is guaranteed to be there with you always whether you use it or not and it will work with iPads and tablets as well.
And nowadays more and more charging hubs are also adding USB ports to support these type of charging dongles. With the overall usability, I think it's a must have in your key ring.
Its available at a price of 29$ with worldwide shipping, but they have an interesting barter service where you can exchange your services for their product. You can also get it 20% cheaper by visiting the link below.
► Nomad Charge Key (20% off)