Warren Taylorwrote a review of Shimano Di2 Inline Wireless Unit - EW-WU111 on September 14, 2017
Familiarity: I've used it several times
I bought this to update and configure my Di2 systeem with my iPhone since I don’t have a computer. I plugged it inline with the main wire from the junction A box and an extra 150mm wire and then used the included clips to secure it to my brakeline. It connected just fine to my iPhone right from the box, and I was then able to update and configure all of my Di2 components.
Connecting it to my Garmin head unit is a nice feature so I can see the battery level. Being able to see what front and rear gears I am in is a nice feature, but I don’t use that feature on my head unit.