Otter Box Commuter case on my iPhone 6+. I get chips and dust stuck to the screen protector occasionally, but the little rubber tabs cover all the I/O ports nicely.
Having a phone on you is a safety thing - not a distraction. You can set it on vibrate and don't have to answer calls. It's for your use in case of an emergency. For that reason, even with wood chips and such, it's nice to have it on your person instead of leaving it behind. Sometimes I leave it on the seat of my tractor while I'm nearby cutting, but I don't always have the tractor with me.