For my Powered Up Conveyex Monorail I need more power than the Hub can give so I've made a Relay that allows me to turn ON/OFF the monorail motors with the Powered Up Hub (using the Handset or a program) but using the Power Functions LiPo battery for the motors, increasing the autonomy of the Hub's 6xAAA batteries: I've made a LDcad model and generated the instructions, they are available at my blog: https://ofalcao.pt/blog/2019/lego-powered-up-relay