I have been down a couple of times in my Rollerblade wristguards, and they're great. They are no where near as bulky as others I see recommended here but they're so easy to wear and THEY WORK because they focus on protecting your wrist not your fingers not the back of your hand. Rollerblades can go about as fast as a wheel and the brand is well known.
https://www.amazon.com/Rollerblade-Bladegear-Wristguard-Protective-Protection/dp/B00BFPGZR6
These 187's are similar, and 187 is a well known roller derby brand. The protection is where you want it, so they're easy to carry easy to wear easy to use your phone.