If a case is like a protective suit for your phone, you can think of Bumpers as the bikini alternative. These are molded plastic guards that wrap around the edge of the iPhone 4, giving it a modest level of protection and keeping your hands off the phone's integrated antennas.
Bumpers are available in multiple colors, and cost $29 each.
If you're interested in using the iPhone 4 for slideshows, video output, or presentations, Apple offers a $30 VGA adapter that can connect to a projector, computer monitor, or many digital televisions. It has a maximum 1,024x768-pixel resolution output, so keep your HD expectations in check.
Composite and component video output cables are also available for purchase. All of the adapters are capable of playing video content (movies, TV shows, video podcasts, YouTube) to your television, provided the connections are compatible.
Apple offers a basic iPhone 4 dock for $29 that includes an audio line output and a 30-pin pass-through connection for connecting to a charging cable, video output cable, or any other accessories that would otherwise plug into the dock connector.
If you've been holding off on upgrading your home wireless router to the 802.11n spec (2.4GHz only), now might be the time to bite the bullet. The iPhone 4 supports the newer, faster Wi-Fi spec, so why not take advantage of it. This is especially true if you plan on making video calls using the new FaceTime feature, since the feature does not yet work via a 3G network.
If you want the ultimate protection for your iPhone 4, why not just leave it in your pocket? By using a high-quality Bluetooth headset, you can make and take crystal clear calls on the iPhone 4 without touching the device.
Sure, you can plug any old pair of headphones into the iPhone 4's 3.5mm headphone jack, but you may as well invest in a pair with a compatible microphone and remote control.
There are tons of third-party headphones with iPhone-iPod-iPad-compatible remote and microphone functionality, but we genuinely think Apple's own In-Ear headphones sound pretty great for the price (about $70).
If you're as fanatical about fitness as you are with your gadgets, the iPhone 4 offers integrated Nike+ software to track your activity. To get it working, you'll need a compatible pair of Nike shoes and the Nike+ shoe sensor ($19).