I have been. Using the Biologic Reecharge for 4 years...It charges my Samung Galaxy Express with no problem....It works best if you start with the battery on the unit charged AND the battery on your phone charged...then just leave it on while ridng and it will actually. OVERCHARGE.....so let the phone drop to 80% and then start the charging...it will charge ...
After several years, many new options for on the bike, turn-by-turn navigation have appeared. These are some of them:
Changing my accepted answer to this one, to reflect the current state of the art.
To avoid changing batteries, you could opt to get an external USB battery pack and power it off of that. That way you could get a continuous stream. If you got a big enough battery pack, you would most likely be able to power the iPhone and GoPro off of a single battery pack provided you found one that was big enough.
Garmin now has a lower cost touring gps that is more suited to navigation than than training. It comes with maps and runs about $250 USD. It's called Garmin Edge Touring. There is a more expensive model which supports a heart rate monitor for about $50 more.
I'm guessing this would work well with software like ridewithgps or garmin connect to plan out ...
Co-Rider app can follow a GPX file from your dropbox account and it also integrates with Ride with GPS for easy access to your saved routes. You can also drop pins and get directions to random points as well. Voice navigation is available, and I've found it useful.
I use my Samsung S2 with an extended-life battery and the fantastic Finn mount. I use Strava and ViewRanger apps (usually both at the same time). The whole setup is very cheap and knocks spots off the single purpose bike computers that I have seen.
I would want to carry a phone anyway, so the weight consideration is entirely in favour of letting the phone ...
You can buy/get an old smartphone, after uninstalling unnecessary software (almost everything) install MMR/endomondo/strava app, insert expired sim card (still connecting to BTS stations - better tracking accuracy) then you have a great cheap bicycle computer with track logging.
I'm using currently using Quad Lock mount with an iPhone5. I'm having no issues with it and the GPS is very accurate. Battery life is still a concern, but turning off LTE, Bluetooth and Wireless, while turning on Do Not Disturb; I'm seeing less then 10% battery usage per hour. I don't have any hardware for it yet, but looking at the new low-power bluetooth ...