I have a hunch, which unfortunately I don't have time to research & turn into a full report at the moment. So rather than let someone else steal my thunder, I'll blog about it instead.
I think the coolest thing about the iPhone isn't the multitouch screen or the industrial design, it's the motion sensor. No, the iPhone isn't alone - the Nokia 5500 has one too ("Nokia plans to introduce other phones that use 3D-motion-sensor technology in the near future"), and I've seen references on the web to some others - in particular, it wouldn't surprise me if some local-only Japanese or Korean devices have them. Then of course there's the Nintendo Wii as well.
I'll take a punt here & predict that motion sensors will become pervasive surprisingly quickly, and that we're only at the tip of the iceberg in understanding the applications. Sure, we know we can use it as a gaming controller, or to detect which way up the screen should be displayed if the device is held horizontally/vertically, or to monitor your sporting achievements. But I reckon there's a lot more to come.
I've seen quite a few references to motion sensors being used to recognise someone's walking pattern. The suggestion is to use this as an anti-theft "locking" function - someone half-inches your dog & bone, and the tea leaf's different gait alerts the phone to prompt you for a password. (OK, sorry about the rhyming slang, it's Friday...).
But I reckon the biggest thing is that it could appeal to operators as well as being used for "local" uses like the ones above. Given that operators specify (and certify and often subsidise) many handsets, having something that has dual-appeal both direct to the end-user for applications, and to the operator for services as well is likely to be a winner. It's why cameras took off (User: takes snaps; Operator (in theory!) gets MMS/email revenue) or even Bluetooth (User: use headset in car safely. Operator: more minutes of use). And it's one of the reasons why WiFi attach rates in handsets haven't grown faster - it's often difficult for the user to exploit the WiFi for their own purposes as well as the operator's (more on this in another post).
So, what could be motion-sensor based services? I reckon it comes back to a theme I'm developing about "context" being more important than "content". If operators get access to the sensor APIs, they could determine a lot more about how you want to communicate. It should be possible for an advanced presence function to have status descriptions like "walking", "on a train", "in a car" and so on. How about a service which uses multi-context data - if the phone's on charge and there's been no vibration consistent with footsteps for an hour, then there's a good probability that the user is either out of the room, or asleep. Or which detects the combination of a car's movement "fingerprint" plus registers a Bluetooth headset being used - inference being that the user won't be able to look at the screen, and therefore sends video calls straight to the mailbox.
These are just of the top of my head. Yes, all of these could suffer horribly from false-positives and false-negatives. I've said before how much I hate technology which tries to second-guess me, unless it's done really well (eg Google's "did you mean...." mistype-correction function).
I'll keep watching on this, as the more I think about it, motion-sensing is a key part of the multicontext environment which will swiftly replace the current narrow obsessions with content & multimedia on mobile devices. If I was part of the Symbian or Windows Mobile teams, I'd make sure I had an open sensor API on my near-term roadmaps, and I'd suggest the JCP gets working on a Java one too....
PS - just noticed that this handset-centric sensor company got more funding 2 weeks ago. Nice to know I'm looking ahead at the same time as the VCs (who include Qualcomm, interestingly)....
PS2 - just seen this very detailed article - if the price point is already at the $2 level, and they look small enough to fit in a phone, I reckon this is a done deal. I can see this getting to 10-20% penetration in the next 3 years, ie >100m devices. Get writing, apps developers.....