Do smart hose timers need a Wi-Fi hub?

It depends on the product. Bluetooth-only timers (like several Orbit B-hyve XD models) work directly from your phone when you're nearby but can't be controlled remotely. Rachio's hose timers and some Orbit models require a separate Wi-Fi hub plugged in indoors to enable remote app control, scheduling on the go, and weather-based skips. If you want to manage watering while away from home, choose a Wi-Fi-hub or Wi-Fi-native system.