Camilo

As an alternative you can add a display unit (MT800 or M9051) that plugs into the junction box and displays both actual battery level and gears and can program the shifting, etc. They also provide wireless commuication to your phone (watch out for the M9050, it doesn't). They are technically MTB units (XT and XTR respectively) but I've seen that roadies use them. Lots of YouTube videos on installation, funtionality, etc. I plan to get one (MT800) for my wife's new Di2 bike that didn't come with the little hidden wireless unit. She doesn't have a fancy computer (like yours truly does), but likes to use the old school Cateye she is familiar with. I've given up trying to get her too much in the weeds with that sort of thing, like getting a bike computer with more features, but she will appreciate a simple display on the handlbars. Might even come to appreciate what the phone app can do. This thing is a little spendy (compared to a Di2 bike? Nah) but should be dead easy to install and use, allows, but doesn't require the use of a phone app or computer, and doesn't require a compatible bike computer.