One of the more interesting things you can do with the iPhone is use it as a remote control for other devices. Since the iPhone App Store launched almost two years ago, developers have created hundreds of remote control applications.
Some of them are for entertainment — designed to control A/V equipment in your living room. Others control household appliances, functions on your computer, or even expensive corporate security systems.
For now, most remote control apps operate over the Internet, or via a wi-fi or Bluetooth link between your iPhone and another device. But one company is developing an infrared iPhone accessory, which will open the doors for even more remote control applications.
It's conceivable that, with these apps and accessories, an iPod touch could replace the fanciest of universal remotes, and have the bonus of shipping with a Web browser and all the other apps on the App Store.
More TV providers are releasing iPhone apps to use as DVR remotes. Recently, Comcast published an app that allows some of its digital cable subscribers program their DVRs remotely. And free apps from DirecTV, DISH Network, and AT&T let you program your digital video recorder from anywhere.
Zipcar rental car
The free Zipcar app lets you find and book rental cars. But the impressive part is that you can also use your iPhone to unlock the car or make its horn beep.
Home lights and automation system
A recent Apple commercial highlights this app for the Schlage LiNK home automation and security systems. You can watch your doors, lock and unlock them, turn lights on and off, etc.
TV, other gadgets
This isn't just an app but a $50 hardware add-on that gives your iPhone infrared support.
When it ships — supposedly soon — the L5 remote accessory will let you turn your iPhone into a universal remote, replacing any number of remote controls that are on your coffee table.
Via Apple's free Remote app, search and change the song playing on your computer's iTunes jukebox from bed, across the house, or even outside. Or change volume settings, or hit pause, etc.
Another app called PodLink ($2.99) lets you wirelessly control music playing on another iPhone or iPod touch, perhaps one that is being played in a docking station across the room.
There's also a $3.99 app to control WinAmp if you use that.
Mouse and keyboard
This is helpful if you want to kick back and don't have a wireless keyboard, or if you're using an old computer hooked up to your TV and want to access the cursor or type something from the couch.
Several Blu-ray discs include Internet features that can be accessed via iPhone apps. For example, the free "pocket BLU" app can act as a remote for Blu-ray discs that support "pocket BLU" — including "Bruno," "Funny People," other movies. Features include controlling playback, browsing through chapters, the soundtrack, etc.
Other Blu-ray remote apps are available for different systems, including the Sony PS3.
Roku video player
If you use a Roku video player — the cheap, no-frills box that plays Netflix, Amazon, MLB.TV videos, etc. — you can get the free Rokumote app and control your Roku without its plastic remote.
Apple's $0.99 Keynote remote lets you control Keynote presentations if you own the iWork suite.
Other apps, like Evan Schoenberg's versatile $0.99 Rowmote can steer PowerPoint slides.
Desktop PC or Mac
This one takes a little tinkering, but free VNC — "virtual network computing" — remote desktop software on your computer (Mac, PC, Linux, etc.) will let you view and control it from anywhere, provided it's turned on and hooked up to the Internet.
If you have a SlingBox — a device designed to let you watch your home TV/cable service from anywhere, over the Internet — you can use your iPhone to watch TV.
The $29.99 SlingPlayer Mobile app recently got an important new feature, which allows you to stream TV from your SlingBox over 3G. Previously, it only worked over wi-fi.
iCarly - Sam's Remote
This one is for the kids: Fans of the cable TV show "iCarly" may appreciate the $1.99 "Sam's Remote" app, which includes sounds from the show.
A $2.99 app called PhotoKeys:Photoshop Remote puts the Adobe Photoshop toolbar on your iPhone. Not for everyone, but could be helpful for some setups.
Apple's free Remote software also controls the Apple TV set-top box, if you have one of those.
A recent update adds a nifty feature that lets you use your iPhone's multi-touch screen as a "gesture pad" to scoot around the Apple TV display. This is much easier than using the small, plastic remote that came with Apple TV.
You can also use the Boxee remote app to remote-control Boxee, if you've loaded that onto your Apple TV.
Sonos Home Stereo
Pro audio software
CPI Security customers can use a free iPhone app (with additional service) to monitor their home security system, turn it on and off, see activity history, etc.
X-Plane Flight Simulator
Sort of like how Nintendo's DS has a touch-sensitive second screen that often controls what's happening on the first screen, this will let you control and observe some of your flight simulator's features — on your computer — using the iPhone as a smaller, second screen.
Ladies: We're not quite sure how this one works, but the $9.99 "Boyfriend remote" app is worth every penny if it performs magic.
You can tell it to "give me money," "forget about beer," and even "take me to the mall." Classy.
(What's Boxee? Think of it as a multimedia-specialized Web browser that you're supposed to steer from your couch. Lets you watch Netflix movies, MLB.TV, and other Web video streams.)
VLC Media Player
Plenty of security camera monitoring apps in the App Store, depending on your rig.
By far the most expensive, though, is Lextech Global Services' $899.99 iRa Pro, which delivers "a video command center to the palm of your hand."
Digital SLR Camera
If you hook your Canon EOS or Nikon DSLR camera up to a computer via USB, you can remotely control settings, fire the shutter release, and see your camera's viewfinder remotely over wi-fi.
The main drawback is that your camera has to be hooked up to a computer.