NumberKey Connect makes a perfect companion to Apple's wireless Bluetooth and laptop keyboards, which lack number keys. It even offers four different themes, and its behind-the-scenes use of Bonjour translates to an automatic and reliable connection for your Macs running 10.5.5 and above, with an iPhone 2.1 or later. Simple in form and execution, this solution is both infinitely useful and potentially prophetic concerning future device interaction.
Of course, there's always full-on computer control, and for that you can use the free Mocha VNC Lite. As long as there's a wireless network connection -- including 3G signal -- and a properly configured Mac or PC, you can access your computer and control it as if you were in front of it, all from your iPhone.
The software provides support for all sorts of interaction using gestures and taps, including different input modes for controlling the screen or for manipulating icons on the computer.
For my part, I've used Mocha a few times to access mission-critical servers, allowing me to input commands via Mocha's on-screen keyboard remotely and helping me avoid a very bad day. At home, I use the software for accessing the Mac that controls my optical disk carousels. With Mocha and some not-so-fancy AppleScript, I can access the Mac to pick one of several hundred movie titles without having to interrupt the current program on screen.
My own examples are just scratching the surface as to what can be done with the ability to control a computer from anywhere you are.
Clearly, these are the first steps for the iPhone in device interactivity. Although the pairing of two wholly different devices to perform a specific task isn't anything new to the computer scene, the iPhone's software platform and wireless connectivity options portend an almost endless array of possibilities.
Note to Apple: For this to truly become the future, you need to open up hardware accessibility to third parties! (Although logic dictates you may already be working on this.)
iPhone + home automation
Apps: iPhone Home Controller 2.0, Smarthome
Imagine being able to read the contents of your fridge by glancing at a list stored on your iPhone; dimming the kitchen lights with a gesture on the touch screen; and finally being able to determine beyond all doubt that you did, in fact, turn the iron off.
As we march into the future, there is an emerging marketplace for mainstream hardware that bridges the gap between the iPhone and household appliances. While direct-connectivity options built into appliances are the next logical step, there are currently third-party options that enable home automation for existing homes.
Be warned, however; home automation is getting better, but it's still all rather geeky and niche-y, complete with dedicated online forums run mostly by über nerds who are to regular nerds what nerds are to normal people. If you're still curious after that caveat, there are a few sites that offer complete solutions, including Smarthome.com and the iPhone Home Controller 2.0.
For examples of home automation via the iPhone, the Smarthome site even offers a Web video that demonstrates dimming lights, turning on and off sprinklers and adjusting temperature. It also shows the ability to monitor all of the actions remotely using an IP-based Web camera.
If you still want more, check out this list of home automation software, compiled specifically for the iPhone, including many more options than I'm able to cover here.