This app was mentioned in 7 comments, with an average of 1.71 upvotes
If you reject the phone call by swipping it just rejects but if you swipe from bottom to up then you have predefined messages that you can send to the caller. There is also an app that can change these predefined answers: https://play.google.com/store/apps/details?id=com.bmc.wearresponses&hl=en
Sounds like this is what they want: https://play.google.com/store/apps/details?id=com.bmc.wearresponses
or Coffee as /u/James-Allenby suggested: https://play.google.com/store/apps/details?id=com.awear.coffee
I think you're looking for this: https://play.google.com/store/apps/details?id=com.bmc.wearresponses
You know you can change responses when texting? Try this app out.https://play.google.com/store/apps/details?id=com.bmc.wearresponses