Like all absent-minded people, I occasionally misplace my iPhone around the house. It's typically just under a cushion after being swallowed by my couch, but I instantly go into panic mode from the insecurity of not having my phone on me at all times.
Before the Apple Watch came out, I'd have to log into iCloud on my computer to play a sound remotely from Find My iPhone. Now I don't have to, because my Apple Watch has something better and more convenient.
Let me clarify that this feature is not similar to the tracking one in Find My iPhone, meaning you can't use it to find a phone you lost during a drunken night out on the town. This feature utilizes the Wi-Fi or the approximately 300-foot Bluetooth connection between your iPhone and Apple Watch.
To ping your iPhone, swipe up on the Watch face to access Glances. From here, just swipe all the way left to the Settings glance where you'll see the Ping option (an iPhone with audio lines). Tap on that.
Regardless of whether it's on silent mode or not, your iPhone will project loud sounds, allowing you to find it in half the time it'd regularly take you with Find My iPhone online.