The killer app for the iPhone is — drum roll, please — the iTunes App Store. Five months after Apple launched its online emporium, I believe it even more, having downloaded a gaggle of programs, including some that transform my iPhone 3G into a harmonica, metric system converter and level.
There are now more than 10,000 of these applications for the original iPhone, its 3G successor and in most cases, for the iPod Touch. Many are free.
I encounter buggy programs from time to time, but there are frequent updates to fix such snags.
And because of the drain on the battery, Apple still won't let developers produce apps that run in the background. So forget about listening to Internet radio while checking e-mail. I'm also waiting on an app that will let you shoot video.
All that said, exploring the App Store on your handheld or via computer is a delight, and you can rely on fellow users for reviews. Some of my favorites:
•Listening to radio. There's a reason Pandora has emerged as the most popular free iPhone application. Type a song or artist's name, and Pandora creates an instant radio station inspired by your selection, same as on a PC or Mac. Fine-tune stations by indicating whether you like what's being played. In some cases, you can buy the music you hear through iTunes.
The iPhone, of course, functions as an iPod. But your storage is limited. If you have gobs of music on your computer, consider Simplify Media. The $3.99 program lets you stream (most of) your music collection and that of up to 30 friends.
Setup is simple, and though music sometimes is slow to start up, it sounds good. Simplify generally worked really well as I rode in and around New York City. (It works on Wi-Fi, 3G or pokier Edge networks.) You can view song lyrics and artist bios. But Simplify can't remotely play iTunes purchases that are DRM or copy protected.
How often have you heard a song on the radio or in a club but didn't know its name? Hold the iPhone up to the radio, and let the free Shazam app identify the tune, usually within 20 seconds. Shazam doesn't get it right every time. But it correctly tagged material as varied as Come On Over from Isobel Campbell & Mark Lanegan and Corcovado from Astrud Gilberto.
•Making music. Smule's addictive 99-cent Ocarina turns the iPhone into the ancient flute-like instrument. You softly blow into the iPhone's microphone and play notes by pressing and holding your fingers over any of four virtual on-screen holes. There are 16 possible combinations, and you can alter the sound by tilting the phone. There's even "sheet music" on Smule's website to play anything from Over the Rainbow to If I Were a Rich Man.
Ocarina is social. Tap a globe icon to rate performances from users around the world. They, in turn, can show you the love.
Or try developer Benjamin McDowell's Harmonica app, also 99 cents. Sure, it's odd putting your mouth on the screen. Fortunately, you can also play with fingers.
•Diversions. I've enjoyed racing games that take advantage of the iPhone motion sensor, including Vivendi's Crash BandicootNitro Kart 3D ($5.99) and Pangea's Cro-Mag Rally ($1.99). I also like Glu Mobile's recent release of a 3D marble puzzle called Bonsai Blast ($3.99).
But as a casual gamer, I gravitate to titles such as Brain Toot (99 cents), which serves up vision, memory and other mind exercises. In one, while being timed, you must pick out the highest or lowest numbers from a series of numbers shown.