Is the cell coverage in your area not up to par? Whether you happen to have steel walls or live where there are no cell phone towers or trees cleverly disguised as cell phone towers, some of us must deal with the reality that, while we own arguably the most innovative gadget in recent years in the iPhone, we may not have had the best carrier to accompany it. One way to address this "bag of hurt" is through the Skype [iTunes link] app.
If you don't already have the Skype app, download it -- it's a free download in the App Store. Next, you'll need to make sure that Skype stays online when the screen is locked. This is accessible via the Skype app preferences within the iPhone's main settings page. After this is enabled, the Skype app continues to run in the background and maintains a Wi-Fi connection even after the sleep/awake button is pushed -- or if it's set to automatically lock after a given time interval. Second, because Skype requires a Wi-Fi connection to make and receive calls, you'll also want to make sure that whatever cell phone dead zone you're at also happens to have a Wi-Fi connection.
This workaround obviously isn't without its weaknesses. Assuming that most of those calling you would prefer dialing a phone number instead of your Skype user name, you'll likely need a separate phone number. One option is SkypeIn, which marries Skype to a real phone number. The service costs $18 for three months or $60 for a whole year. And if you happen to have a Google Voice phone number, directing your calls to your SkypeIn number is an option. Alternatively, you could forward all of your iPhone calls to said Skype number whenever you anticipate a cell phone dead zone -- say, before you enter your house, if you have bad reception there. This is accessible via the Phone preferences within the iPhone's main settings page. Doing this, you won't have to give out multiple numbers to your friends and family.
One of the other drawbacks of this alternative is that while an audible indicator (a ringing noise) is present when you're receiving a call, a visual one isn't. In other words, you may need some cat-like ears to know when you're receiving a call.
A seamless solution this is not, but it nonetheless provides a possible workaround until more cell towers are built in your area, or until a push-based solution is available for Skype.
Readers, tell us what you're doing to remedy cell reception issues. Be it a do-it-yourself tin can signal booster or anything else, let us know what's worked for you.