One of the most popular third-party apps for Android Wear is Wear Mini Launcher. As the name implies, it's an app launcher for your watch that tries to improve upon the normal basic list of apps. But as of the latest update, Wear Mini Launcher has started pushing pop-up ads.
A popup from Wear Mini Launcher (image credit)
After updating to the newest version, many users are reporting pop-ups for various sketchy apps, like a cleaner application in the above screenshot. As if that wasn't bad enough, the app also constantly sends out push notification ads. As you can imagine, the Play Store reviews aren't pretty: