What's a good iOS app for keeping track of speed when I'm driving to different clinic locations? Something that's actually reliable and doesn't drain my battery?

Okay, so I'm constantly driving between different clinics and sometimes even doing home visits, and I needed something that was, like, a pocket reference guide for my speed. I'm too tired to learn complicated apps, but this GPS Speedometer app is actually reliable. It hasn't crashed once in the last six months, which is saying something. It just sits there, does its job, and doesn't bother me. The display is big and clear, which is great because I don't want to squint after a 12-hour shift. I mostly use it to make sure I'm not accidentally speeding in school zones, especially early in the morning. It's simple, but it works when you need it, and that's what matters. No extra bells and whistles, just the speed, which is perfect for my needs.