The Treo has a physical slider to quickly let you switch calls on and off. Hardly earth-shattering. but consider this: apparently no other smartphone has that same feature! Now, I haven’t investigated and I’m not enough a gadget freak to do so, but at least it’s what the Treo Director of Product Marketing claims:

During one design meeting, “Jeff Hawkins, [inventor of the Palm Pilot, Palm and Handspring co-founder], said he wanted a way to turn off the ringer and other sounds quickly, and a slider switch just seemed like the obvious idea … What really surprised us, I think, was realizing later that other cell phones didn’t have this feature, and moreover, I continue to be surprised, given how useful that little switch is, that no company I know of has copied it!

It does seem kind of obvious and it certainly beats holding down some random key for some random period of time. (“Sir, the manual makes it very clear that you hold down the ‘8’ button for 4 seconds”).

Following the principle of encapsulation, there’s work being done to let the phone manage the ring-tone for you. I think some products actually try to do this now, but I couldn’t find them. A few cues I’ve heard about:

• Diary: Your smart-phone theoretically knows when you have an appointment.
• Microphone: At the very least, your smart-phone knows how loud it is, so can set the ringer volume. In a more AI scenario, it might also try to work out what’s going on and whether it should be off altogether.
• Usage logs: If you’ve used the phone recently, it’s more likely the ringer should be on. If you’ve taken calls at the same time for the past four weeks, it should probably be on.

So, ultimately, there needs to be a third slider setting: on, off, and you-tell-me.