Would be interesting if non-partied players in the area could make noise upon entering the player's "area of view".
In the forest, a gentle crack of a twig. On quarries the sound of a kicked stone tumbling down a slope. On pavement the sound of a boot scuffing the hard stone tiling.
The chance of hearing the noise could be equipment and proficiency check based. Soft moccasins would severely reduce the chance of making noise, but would give up the combat advantage provided by other harder, european soled shoes. The hearing check based on Frontiers and Wilderness, while the sneaking check would be Cloak and Dagger.
With player radar, this isn't exactly a crucial element of gameplay. But often people working in town don't notice a warparty creeping up to their walls, and semi afk characters would have something to perhaps catch their attention if they were looking off the screen. Mostly, it's an atmospheric addition to gameplay, and it would fit nicely into proficiencies being for non-critical, but helpful elements of gameplay.