Wear Charging Widget (com.vuxia.wearchargingwidget) on Google Play
This app will be launched automatically when your put your watch on charge.It will display usefull informations like time, date, weather, battery charge...It will notify your phone when the charge is complete !The screen will remain ON all the time, but a built-in feature protect it from bur-in and marks :)It's also customomisable to match every position and wear watches !