As many other questions here on SO, I encounter a similar error message. Unlike other questions, this is regarding a hardware debugged device.
My gradle wear-build file looks like this:
compile fileTree(dir: 'libs', include: ['*.jar'])
W/GooglePlayServicesUtil: Google Play services out of date. Requires 8298000 but found 8107534
Google Play Services is not going to be bundled with your app so what you are seeing is that your watch is using version 8.1 of the Play Services (which is installed on your watch) and you compiled your app with a higher version and that is not going to work; the version installed on your watch should always be bigger than or equal to the version you compiled your app with (same is true for your phone)