The key is that the barrier to entry is now so low, that innovation can prosper without significant drag or hindrance.
So why don't we open the hardware on smart phones, by offering a "geek port" that some nice simple interfaces and a really cheap common connector, like a female .156" DIP header?
The port could have some analog and digital input and output lines, and maybe a serial interface or two, perhaps the common SPI interface, and a 3.3v power rail (that the phone can turn on and off to control power consumption).
Such a simple port would be trivial in cost to add to smart phone, probably costing less than $1 in marginal hardware cost, plus a once-of cost developing some nice APIs to access the port.
Creating such a simple interface would allow the creation of cheap dumb devices that can plug into the port.
Really boring stuff, like, say, a digital thermometer, an LED and sensor that can be used to collect pulse oximetry data, and relay it on an infrastructure-independent mesh network like servalproject.org, to a local care provider. Or maybe it might be a cheap ultrasound transponder to allow mid-wives and maternal health workers to acquire cheap ultrasound imagery.
Each of these plug-ons could probably be made for $5 or less, and yet each has the potential to save many lives in the developing world, and save many billions of dollars in the developed world.
And that is just in one application domain. Who knows what else people might come up with.
After all, no one anticipated the myriad applications that have been enabled by making smart phones programmable.
I reckon that for perhaps $100,000 it would be possible to get a phone designed and a small manufacture run of such phones to demonstrate the idea. Anyone want to make a significant impact on the world?