My favorite biking accessory is my Quadlock - https://www.quadlockcase.com/. Having my phone securely mounted on my handlebars is a game changer. If I want maps, I have those up. On longer rides, I have my phone playing music directly from the phone speaker which I actually like more than using headphones. I also have my heart rate monitor connected to my phone so I can see those stats if I want them. My bike feels like a Tesla with a touchscreen on it.