Make ringers “polite.” If a phone ‘rings out’ (e.g., rings non-stop until voicemail kicks in), switch to silent mode automatically.
Yes, this has flaws, like missing multiple calls because you missed one call.
But sit here with my as my suitemate’s phone rings time and time again, with a really irritating ringtone while he’s gone, and hold back the tears long enough to tell me that this feature isn’t necessary.
If nothing else, come up with a universal, unobtrusive means of switching a phone to silent. My Treo’s got a slide on the top, and I think all phones should have something like that. Every time I try to use someone else’s phone I end up getting into strange menus or, more often than seems statistically probable, ending up inside a web browser. So I’m pretty averse to opening up people’s phones and changing settings. I could cope with sliding a hard switch on the outside, though.
Seriously, please implement this. I’m begging.