Re: Why would you need a dock?
Mr Clark, An S5 you say? You early adopting fashion-victim hipster!
I had to get a replacement when my S4 Mini got nicked. MHL was the reason for going with a second-hand, reconditioned S5. I have since splashed out on an SD card, the MHL connector, wireless charging kit, a second battery an OtterBox and Quadlock combi for mounting on the bike.
TBH I think whines about fixed batteries are over done. For heavy use you can just take one of 6000 mAH packs with you.
Anyway, got to go and wax my moustaches! ;-)