Hey we can put messages through esp32 but you can set reminders on your band or watch. And also you can send messages to watch or band through an app called noti notes. To send messages you have to enable noti notes app to push notifications on your device and Just type what ever you want to write on noti notes app and see the message . Its just like a notification like WhatsApp or Twitter but it's custom .or you can use notify for mi band app