AfterShokz sent me a pair of their Aeropex Bone Conduction Headphones ($160) to try this summer, and I've relied on them for every run since. The speakers sit outside your ears and transmit sound through your cheekbones to your inner ears. Your ear canals are uncovered, which lets you hear ambient sound and helped me, at least, feel safer and more aware on my runs, making this a very useful gift for any runner.