OS 14.4 Developer Beta 2
The main features you’ll see in this beta are new functionality for the HomePod mini and its U1 ultra wideband chip used for location awareness. When you use Handoff to transfer a song to and from your HomePod and iPhone, there will be new haptic, audio, and visual effects. iPhones 11 and 12 have this U1 chip.
As u/kyemaloy14 shared, when the HomePod mini detects an iPhone nearby, the iPhone will register a haptic rhythm that gets faster as the iPhone gets closer. When the iPhone is almost touching the speaker, the song transfer banner will expand and transfer the music.
Additionally there is a new walking workout feature in the Apple Watch app on the iPhone. Called “Time to Walk” iOS 14.4 adds a toggle to turn on “Add Newest Workouts to Watch”. Rumors speculate that Apple plans to add guided walking workouts to watchOS 7.3.