Easy.....one, it is a PHONE, a primary communications device whose battery will get chewed to pieces trying to get Bob to his meeting where his phone is now dead and unable to send/receive calls or emails (its secondary purpose).
Assuming you run it on battery only while attempting to use the navigation function.
Two.....almost anything "dedicated" has the ability to be better customized for its function, period.
I can make a similar QED statement (almost anything "programmable" has the ability to better customized for a variety of functions, period), but I won't.
Systems follow a model that is based on underlying architecture. When the architecture is weak (usually when the idea is first conceieved), your assertion is
generally true. Why? Because the underlying architecture needed to support the system is completely consumed by supporting the limited functions of the system. However, as architectures evolve, the amount of architecture dedicated to the limited functions of the system decreases, leaving you with two options: generalize and abstract (make the architecture run more systems), or enhance and evolve (add more features to the system to consume the newfound "extra" architecture).
Convergence is best supported by the former: the underlying architecture (operating system, hardware, memory, supporting networks) have evolved to such a point that I can perform the functions of a standard navigation GPS within the excess processing capacity offered by a telephone, personal computer, or other mobility device. When I present a generalized and abstracted environment to a systems developer, the work they need to do becomes more focused on the system, and less on the architecture. This has the effect of lowering cost or increasing features (sometimes, both). I can do this while leveraging the synergies offered between the multitude of systems running on the architecture: cellular modem, data sharing, data storage, touch screen, text-to-speech synthesis, and so on.
So rather than GRMN investing a boatload to design and implement an architecture that can do all of those things (over the air data update, share data with other components of the system, use a touch screen, say "Turn right, 1 mile"), an application developer who understands the math and logic behind navigation can instead focus on the math and logic of navigation, not why a touch force of .2psi doesn't click the "Next turn" icon on the screen, and the hardware is overheating every time I try and have the software convert text-to-speech.
In closing, when the underlying architectures become so powerful that you can simply port the logic into them, and presto-chango the whole package works, then the need for dedicated devices falls through the floor, and exists only in extreme edge cases (for example, aviation approach-certified moving-map GPS). Convergence renders your assertion
false, when it really works (like synergy in M&A transactions), which is what Android + the latest batch of high-horsepower architectures offer.
Three.....unless one gets a holder for the phone to set on your dash, you now have an additional distraction in the vehicle as one looks down at ones hand to figure out were one is going. (Voice or not, people have a tendency to LOOK at the GPS)
From
http://www.engadget.com/photos/motorola-droid-car-and-home-docks-hands-on/2401471/ :
As the iPhone has proved, some convergence is nice, but the battery drain/short charge life is a real pain when one is trying to do things with their PHONE as a phone if they suck all the juice using the ancillary features. Of course you can follow Apples advise and simply not utilize those features/turn them off, then again why the hell buy a convergence device if you have to do that to conserve battery life?
Battery life is, indeed, a problem. Battery research is a very hot area right now, with lots of VC, PE, DARPA, and other monies flowing into startups and university research programs. Hell, Evo Morales, the prime minister of Boliva who is a chum of Fidel and Hugo, may be made to look like the greatest leader Boliva has ever seen: Boliva has access to 70% of the worlds lithium (via lithium that is "mixed in" with their famous salt flats, at the surface and "easily" extractable). In translation, there's a lot of really interesting stuff here, and your quibbles about battery are spot on.
But, like any other electronic device, we only rely on battery when we absolutely have to. Ergo, the Motorola Droid can run on vehicle power while in navigation mode (just like your iPhone, or other device, can).
Cheers,
-Andrew
