I've always used a Fitletic belt when I had a smaller iPhone since the main problem w/ fanny packs in general is the bouncing. I just received the Fitletic Double which does fit the iPhone 6 Plus in the larger zip pocket but barely. I do have a case on my iPhone though. Still hoping for an updated Fitletic belt since the two models that fit the iPhone 6 do not have the race bib holders.
Empty
Tight fit
With iPhone in it. Bulges out a bit.
Empty
Tight fit
With iPhone in it. Bulges out a bit.