Now that I have an Apple Watch I find I pay less attention to where I set my iPhone at home, which means I'm regularly forgetting where it is. Luckily, Apple Watch has a simple Find My iPhone-like Ping feature that makes it easy to figure out where you left your phone.
Use Apple Watch's Ping feature to find your iPhone
Instead of showing where your iPhone is in Maps, just sets off the Ping alarm so you listen to find your phone. To ping your iPhone from your Apple Watch swipe up on the clock face to show Glances, then swipe left or right to the Settings Glance. Now tap the Ping button to set off the alarm sound on your iPhone.
Pinging your iPhone from your Apple Watch works even if your phone is in vibrate mode or Do Not Disturb mode. It won't, however, work in Airplane Mode because the radios that let your devices talk to each other are shut off.
I've found my iPhone buried on my desk, on the couch, in a coat pocket, and in my computer bag thanks to my Apple Watch. It even works if your iPhone is in the fridge. You can trust me on that.