Yes, your iPhone might be able to help you repel mosquitoes, naturally. The Anti Mosquito -- Sonic Repeller is a free app that produces a high-frequency sound, called Ultra Sound, that humans can't hear but mosquitoes find annoying. When you turn on the app, the theory is the Ultra Sound keeps mosquitoes away. While the jury is still out if this works as effectively as chemical sprays, what's the harm? It's free, and all you have to do is turn it on the next time you're outside.