Not all platforms are as open. Apple TV, for instance, is willing to accept encrypted content that mirrors your iPad screen via AirPlay. It's not the same as writing your own code, but maybe someday, Apple will open up a TV App Store.
Emerging development platform No. 3: Your clothing
It may be made of cloth today, but there's no reason why your garments can't be one of the next great development platforms. We take our clothes everywhere, and electronics are now small enough to be sewn in without being noticeable.
There are already early experiments in garment hacking. Scott eVests and jackets are prized because they were designed to hide wires. You can put your iPod in a pocket, and the wires carrying your earbuds are threaded through channels so that they pop out of the cloth near your ears. They're not constantly getting tangled or misplaced -- unless you forget where you left your jacket.
One jacket from Hammacher Schlemer has a "five-button control system woven into the outer sleeve" so that you can change tracks without taking off your gloves or removing your iPod from your pocket. The buttons lock up after a few seconds to prevent an errant bump from shifting items.
The simplest way to experiment may be with one of the Anduino chips embraced by the Maker community. The LilyPad chip set is already designed to be sewn into clothes; just add LEDs and the right software.
The first adopters may be people who want to program their clothes to change color or patterns to music, mood, weather, or, say, a command sent by the advertising company that purchased the space on your sweatshirt. These apps will be able to communicate with people near us, and they'll enable a new twist to the fashion industry, with artists being able to upload new patterns and wearers able to swap them. People wouldn't ask where you bought that shirt; they would just download the pattern from their friend at that moment. The friend might even get a commission.
That's just cosmetic. Our clothes are always with us, so they may make a better place to put our electronic wallet than in our cellphones. Apps could follow our schedule and zap us if we forget an important taks, like taking our medicine. We may not feel the rumble from a cellphone, but our clothes are much closer.
Emerging development platform No. 4: The electrical grid
In much of the Western world, electricity is so stable that it's boring: Plug your device into the wall and it works. A month later you get a bill, and after you pay it -- as they say in the country music business -- the circuit remains unbroken.
But there's no reason why we can't enjoy a much richer, more sophisticated electrical grid with flexible pricing, self-healing circuits, and an app market full of opportunities. Filtrete, for instance, offers a programmable thermostat that is Wi-Fi-enabled and ready for remote access.
Many appliances are already integrated. The X10 standard has been widely used for home automation for some time, and libraries for languages like Java are common. Some controllers, such as Insteon, have built-in Web servers that let you interact with devices by POSTing data to the URLs.
There are more complex APIs. The ZigBee standard is growing increasingly common because it offers a more elaborate, energy-savvy API for making decisions about energy use.