You can certainly run a long-distance race without a smart watch, but I have found my Apple Watch Series 3 ($189) to be a game-changer in terms of prepping for my half marathon. Yes, it's expensive, but it helps me easily track my mileage and keep track of my pace. Since my Nike Run Club app connects to my Apple Watch, it helps me track my distance and speed. Plus, I can change the songs on my Spotify playlist directly from my watch.