Last night I finished fitting a Battery Tender weatherproof USB point under the LHS part of the dash/fairing and a dual USB outlet/voltage meter where the power socket accessory goes, both wired in to the accessory connector at the front of the bike and on their own fuses (so one blowing doesn't affect the other - in theory). Jon Long's video is superb for showing how to do this.
As my bike is tourer spec, my plan is to next buy a weatherproof case for my phone to fit the supplied mount and run a cable from the waterproof USB point under the dash to it for day-to-day then use the dual-outlet for when I eventually get a GoPro or similar.
The price of the Kwak accessory seems really high. I got everything I needed for less, including both USB points, wire, fuses, Anker cable, crimps, crimping tool, heat-shrink tubing, everything!